Its no longer listed as "My Controls."
Scroll up to the top of the page, look above where it says "Welcome, MissusF" and click the link that says "UserCP." Scroll down the page that takes you to until you get to an see "Edit Signature" on the left.
JM uses BBCode which means you need the codes that have [/] around them, not html which uses </>.
I see you've done your avatar already so I hope that answers your question.