I want to use my signature as link on this forum. After how much time and post I can use signature links on this forum.
You have to wait 90 days after signing up. Please check out the FAQ for more infofmation.
Like he said, you'll get no backlink/SEO benefit. You're welcome to advertise your site, but if you're posting just to pimp your links, please don't bother.
If you're posting to learn/share knowledge, then by all means, welcome!
You have to wait 90 days from the date you signed up to get your signature. See here: SitePoint Forums - FAQ: Your account and profile.
If your looking for backlinks, sig links on this forum will gain you zero. Everything here is rel="nofollow".