To add a signature like mine include the url tag.  For instance, to link to my profile, I use this: [url=http://deckbox.org/users/qwerty59]Profile[/url]

Basically, this takes the format: [url= {Wherever you want to go} ] {Whatever you want to call it} [/url]

So, if I wanted to link to google I'd use:
[url=http://www.google.com]Google[/url]



My current signature is like this:
[url=http://deckbox.org/users/qwerty59]Profile[/url] | [url=http://deckbox.org/sets/43955]Tradelist[/url] | [url=http://deckbox.org/sets/43956]Wishlist (High Priority)[/url], [url=http://deckbox.org/sets/281503]Wishlist (Generally Interested)[/url]