First upload your sig to some hosting service like photobucket.com or imageshack.com.
Then in Profile=>Signature put url to that image inside img tags.
eg
- Code:
-
[img]http://i75.photobucket.com/albums/i293/Desertus/sig_v3.jpg[/img]
.
Then in Profile=>Preferences=>"Always attach my signature :" pick Yes.