You can edit or delete the comments that you have posted on your video or another user's video. To edit the comment you've given, go to the comment, then click on the pencil icon underneath your name. This will open a box that allows you to edit your comment. Once you are done editing your comment, click the blue check mark to post it.
To delete a comment, go to the comment, then click on the trashcan icon underneath your name. A warning box will pop up that lets you know that you can't recover the comment once it has been deleted. When you click 'Delete Comment,' it will be deleted from the video.