Yuku free message boards

Adding a signature varies depending on the forum software being used. Here on ez-board:
1) click on My Control Center (the link is under the Thorn News & Discussion Page logo on the main forum screen)
2) click on Account Preferences (in the center of a group of links near the top of the Control Center page)
3) under Posting & Messaging, check the box for Use Custom Signature
4) add the URL in the signature in the box provided. You could probably include it either as the raw URL, or you could use HTML tags or EZ Codes to tag your URL as a hyperlink. (See the link in my signature to my ancient guitars page as an example. Note the page itself is nothing special, but you get the idea for how it works)
5) Click the green Save Changes button at the bottom of the Account Preferences page.

Once you're done, try a new post and verify that your link appears and resolves correctly. I think that's all you need.

I should note that search engines like Google work by crawling many, many Websites on the Internet and then building an index that they use to return search results (and rank pages, etc...). Google does not crawl every page on the Internet, so if the forums where you leave your links don't get crawled this method may not help. There are a number of reasons for that, but I'd be going way off topic to get into details. That said, it's a good idea and should be an easy way to at least advertise your site. Hope this helps!