If you're still within the 4-hour window and your post is a reply, not a new thread, the Edit button also offers you a Delete option. For threads, you can take out the content as Indie suggested and use the "Report" button (the or icon at the left of every post) to ask one of us to get rid of the thread for you.

If it's too late to edit, all you can do is report the post as above.

When the top post of a thread is removed, any replies go with it.