You can edit or delete your own posts. Of course, you must be logged on to do this. Then, go to the specific post you want to edit or delete. To edit, click on the Modify button. To delete, click on the Delete button. Both buttons appear at the upper right corner of your message.
I would hope you don't go back to any of your original posts and delete them. That ruins the discussion since viewers can no longer see the original post to which replies were posted.
I don't know about completely removing yourself. Why would you want to do this?
Edit: I just saw how you can completely remove yourself. Go to your Profile modification panel. At the bottom, you will see a button for Delete User.
