You may have to edit a post or comment because of a spelling error, to add something or remove something, embed a vid, add a photo/GIF.
The Circle app does not have that option, thus it can only be done through a browser (on PC, phone, tablet).
Open your post or scroll to your comment. Tap or click the 3 dots (…) and select edit xxx, then you can edit your post or comment.
Then select “Save changes” after it is done.