Go to your user CP (top left)
Edit Signature
About half way down the page you will see a box with lots of symbols
Look for the one that looks like a mountain (its on the second line down under the undo button) and click on it
A new box will open, press CTRL +V to paste the code directly into this box
Scroll down a little and preview signatre (the sig will appear in the top box) If it doesnt its gone wrong!