Go to your gallery menu on the left and click on Client Options.

From the Client Options settings, click on the Comments tab.
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Under the Comments header, select the comment that you want to view.

Use the Add a Comment field on the right to reply to a comment.

Select the comment in the comments list that you want to delete.

Hover over the comment on the right side of your name (or the left side of the commenter's name) and click on the trash can icon.

A dialog box with the text Are you sure? will pop up. Click on the OK button.