It’s pretty simple.
Here’s a comment I left the other day:
When I hover the mouse cursor over on the right side of my comment, a pencil icon appears.
If I continue to hover there, a screen tip will appear that tells me I can edit or delete the comment.
When I click on the pencil the option menu appears.
Clicking on edit opens up the comment box for me to make changes.
After I make the changes, and hit enter, the changes appear with the comment. As well, the word “edited” appears on the line below the comment.