Basically, you put the code: [url=x][img]x[/img] into your sig tab. Replace the x with the URL and the Image link

E.g. [url=http://theotaku.com/worlds/deadfrontierworld][img height=275 width=512]http://i1336.photobucket.com/albums/o650/haoliu/MySig_zpscaf79aa5.jpg[/img][/ url]

If you don't know where your sig tab is, follow these steps:
1. GO to my Profile
2. Go to Profile Information
3. Scroll down and you'll find the word "Signature"
4. Copy and paste you own sig images or write a text into the sig tab.

This is where it is:

Special Thanks to Nyra for helping me :)