Pretty much just take the url, or address from the address bar of the page you want, for this I will be using my Profile.
http://www.gaiaonline.com/profiles/?u=6856282


And the IMG code for the picture, most likely off of Photobucket or if you need to you can always add your own img tags. Simply put [img ] before the Url, and [/ img] after the picture Url... For that I will use a random meaningless picture.
[img]http://i170.photobucket.com/albums/u249/Hardfang/fluffythedestroyer.jpg[/img]


Next we add them together like so-

And this is were the pictures url goes. And then close the url.

When you put that together, with the actual link, and image it should look like this.
[url=http://www.gaiaonline.com/profiles/?u=6856282][img]http://i170.photobucket.com/albums/u249/Hardfang/fluffythedestroyer.jpg[/img][/url]



THANK YOU VERY MUCH TO KENJI-SAN FOR THE EXPLANATION