As H3rmit and mazing said, you can edit your own posts for four hours after you submit them. After that, a moderator or administrator would need to do the editing for you. The quickest way to let us know is by reporting the post with the button but you could also PM one of us if you wanted to: Moderators and Administrators.

We'll delete a post (or even a few posts) if you ask us to. If you want a post edited, not just deleted, please tell us the changes you want us to make to it -- preferably exactly what you want the new version to say.