You can use the red and white triangle button beneath your username on posts, to report a thread you want deleted. Or you can post a thread in the "ask the staff" sub-forum asking for it to be deleted.
Remember we only delete threads in very (and few) specific cases, for example, when there is a security risk involved with the information shared in the thread. A thread may be useful to other people besides the Threadstarter, and, thus, we usually don't delete threads if there is no risk involved.
