You need to know the basics of the VoiceOver rotor gesture to use these instructions. If you don't feel confident about the rotor please read my page describing the rotor first.
You also need to be clear about the insertion point. When you are entering or editing text,nnew text is entered after the insertion point. After you enter text, the insertion point will always be at the end of that text. In order to edit text you need to learn how to move the insertion point to the position where edits are required. The insertion point is displayed visually as a flashing vertical line.
You also need to know that the Delete key on the keyboard deletes the character to the left of, that is before, the insertion point. What you hear when a character is deleted will depend on your Deleting Text setting in Settings / Accessibility / VoiceOver /Verbosity. Many readers will be using what VoiceOver calls standard typing, in which you need to locate a character on the onscreen keyboard, lift your finger and then double tap to enter the character. Using standard typing you can delete multiple characters by touching the Delete key once and then double tapping repeatedly. You will hear each character spoken as it is deleted and the verbosity setting determines if anything else is heard to confirm the deletion before the character is spoken. The available choices are:
speak, which speaks the word "delete" before the deleted character is spoken
play sound, which plays a little sound before the deleted character is spoken
change pitch, which lowers the pitch of the spoken deleted character
do nothing, which plays no additional sound.
If your typing style is set to touch typing you will need to touch and hear the Delete key spoken before lifting your finger for every character deletion so any additional confirmation is unnecessary and you may want to set the verbosity to "do nothing".
When VoiceOver is focused on a text field that is being edited a one finger double tap moves the insertion point from the end of text to the beginning of text and will alternate between beginning and end if you repeat the double tap. If the insertion point was initially inside a line of text, the first double tap will usually move the insertion point to the beginning of that line.
Turning the rotor to lines, words or characters will allow you to move the insertion point through text one line, word or character at a time by swiping down with one finger to move forward and up with one finger to move back. VoiceOver speaks the text over which you move the pointer.
After you swipe down to move forward through text, the insertion point will be placed after the text that is spoken.
After you swipe up to move backwards through text, the insertion point will be placed before the text that is spoken.
So, when the rotor is set to lines and you swipe down, the insertion point will be placed at the end of the line that is spoken and if you swipe up the insertion point will be placed before the first character in the line.
It's the same for the words and characters rotor positions; the insertion point will be placed immediately after the spoken word or character after s wipe down and immediately before the spoken word or character if you swipe up.
Just for completeness, there is also a Misspelt Words option on the rotor which can sometimes be useful; I have found that it isn't very reliable and I don't cover it here.
Dictated text often contains errors and you may have spotted these when VoiceOver spoke the text back to you. Voiceover's simple text editing tools will often suffice to make the necessary corrections. I'll describe a typical sequence below. As you become familiar with the tools you'll probably develop your own preferred ways of editing.
Most people find it easiest to edit text by working forwards from the beginning rather than backwards from the end. After your dictation, the insertion point will be at the end of your dictated text. A single finger double tap will move the insertion point to the start of the text.
Unless your text is very short, turn the rotor to lines and swipe down with one finger to listen to your text line by line. Pause when you hear the first line containing errors. Now swipe up with one finger to move the insertion point to the beginning of that line. Let's assume you need to replace one incorrect word. Turn the rotor to words and swipe down repeatedly until you hear the incorrect word spoken. The insertion point will now be at the end of that word so the word may be deleted using the delete key on the keyboard to remove the word letter by letter. When the word has been deleted you can dictate or type its replacement. If the text contains other errors you might wish to turn the rotor back to lines to move to the next line with errors and repeat the correction proces until all errors are fixed. You might then double tap with one finger to move the insertion point to the beginning of the text and swipe down with two fingers to hear the text spoken and check the corrected text.
Spelling within words may be changed using the characters position on the rotor. You can use the lines and words positions on the rotor to move the insertion point to the beginning of a misspelt word and then turn the rotor to characters in order to place the insertion point to a desired position within the word where you can add or delete characters as necessary. The behaviour of the insertion point is the same as for lines and words; it is positioned after the spoken character if you swipe down to move forward over it and it is positioned before the spoken character if you swipe up to move backwards over it. After entering corrections using the onscreen keyboard VoiceOver will remain focused on the keyboard and you will need to locate and touch the text field if you want to use the double tap gesture too move the insertion point back to the start of the text.
The technique for correcting text entered on the keyboard is much the same as for dictated text but there is one important difference. When you type on the onscreen keyboard, VoiceOver will be focused on the keyboard and not on the text you are entering. If you want to use a double tap to move the insertion point back to the beginning of the text you must locate and touch the text field first and you will usually hear VoiceOver speak "text field, is editing".
The section on advanced VoiceOver editing describes some more powerful editing tools including how to select text and copy and paste. These tools will be required for editing that goes beyond a few minor corrections.