Can any friend tell me how to attach your signature? Thanks in advance.

I think you are talking about the signature attached to the bottom of your posts? I clicked this link and scrolled down the page about half way and saw a "Signature" box.

http://www.cctvforum.com/profile.php?mode=editprofile

There maybe some limitations like adding links and such because of your new member status. The site has had problems with spam postings in the past. Once you have 5 or 10 posts the limitations are lifted.