This was created for another forum by me but the buttons are still mosty the same in the words so here it is:
Create a signiture on whatever
My example:
Save it on paint and then go onto ImageShack
Copy the top link when it says "done" by pressing Ctrl C
Then go on here and click "Profile"
Then go on preferences
Click always attach my signiture
Then go on signiture
Go into the white box and click Ctrl V to paste the imageshack link in the white box
Then press Save and it should be there!