cal336

I was having trouble finding how to edit my signature as well. You click your username in the top right corner, click "Account Settings" in the drop down, and once the next page loads, there should be an option that says "Signature" on the left column.

This signature option didn't show up on my left column for a long time, though. It was just the "Overview" and "Recently used devices" tab.  It randomly appeared after about 30 minutes of searching  

There must be a bug on the website... I hope the option appears for you soon!

Just testing my signature