STEP 1: Click on the profile tab near the top of the screen
STEP 2: Click on the signature tab just above you info
STEP 3: Place your the url of your image between the img brackets in the box below
STEP 4: Click the preferences tab above your sig
STEP 5: Where it says "Always attach my signature" Click yes
STEP 6: Click save near the bottom of the screen and your done