There are two ways to create content that links back to your site. The first is to simply put a link in your content at the top or bottom that says something like, "This post was originally on my blog BoyHowdyAdoption.com." And make the url link. (Up at the top of the content area is a button with links on it, press it to make a link.)

The other way is to add a bio that will appear at the bottom of any content you create (not comments or forum posts -- it will show up on pages and blog posts). You can see what mine looks like here.

To do that, go to "My Account" and choose the "Edit" tab. Scroll down to "Additional User Info." Type whatever you'd like into that box and it'll show up in your "About the Author" box at the bottom of your content.

(While you're there you can add a signature to appear on forum posts.)