On your very first post.. use the 'edit this' function. Once there.. there should be an option to delete the thread.
If not, try the 'Thread Tools' to your upper right (must be IN the thread to delete).
IF there are other posts in the thread, I believe the option isn't going to be there (speculating on my part). If that's the case, just PM a mod and we can kill it/lock it for you