how do you get to the edit button in messages

The "Edit" button will not even appear unless all of the following conditions are met:

1) iOS 16 must be installed on the phone

2) The message(s) have been deleted......after.....iOS 16 was installed on the phone

3) No more than 30 days have passed since the message(s) were deleted

Assuming that you have iOS 16 installed on the phone, open Messages and then delete a message that you do not need. Now check to see that the Edit button appears and you can tap Edit to display the deleted message with options to recover the message or permanently delete it.

The Edit button is at the top left of the main screen when you open the Messages app. Also see: Delete and recover messages on your iPhone or iPad - Apple Support

If you are filtering messages, the word Filter is shown at the top left of that screen instead of Edit. Tap Filter to get to the option to edit/recover messages.

Block, filter, and report messages on iPhone - Apple Support