I want to use a picture as a link to a website. I have NO idea how to do this with BB code though. Can anyone help?

if this is in your siggy, you want to go to "edit signature" under the control panel first. regarless, this is what you'll do...

use the hyperlink button (it looks like a lil globe with a chain) in the toolbar above the text box. when you click it, it will ask you to enter the URL of your link.
Enter the web address and click okay.

the clickable link will be formatted. you'll see some highlighted text (usually says the same thing as your URL). ensure that your picture code is an [IMG] format (you can use photobucket to upload your picture if you need to).

Copy and paste that [IMG] code where the highlighted text was.

you're done! if this is in your siggy, be SURE you click Save before leaving the page, you don't want all your hardwork to go to waste!

hope this works for you. PM me if you have any trouble!