Step 1: Go to user CP up there in the left corner of screen
Step 2: On the left hand side of screen you'll see Control Panel Settings and Options.
Step 3: Hit "Edit Signature"
Step 4: There's a little yellow button with mountains on it right next to the little icon of the world (do you see it up there?). This is the Insert image button.
Step 5: A window will appear, and you just type in the text to be formatted. I think it makes you do it twice.
Step 6: Push the "Save Signature" button at the bottom of the page. Refresh your browser and volia!