We'll do this anyway: never hurts - -
In the upper right corner, you see the circle with your profile name. Click that and choose "EDIT PROFILE" from the drop down.
On the next screen, on the left side, you'll see a menu. Click on ACCOUNT, but you want the one in the bottom list (under FORUM). Scroll down the page, and you'll see EDIT SIGNATURE. It's about halfway down near "Conversation Detail Options."
When you select EDIT SIGNATURE, you can then type into the editor much like posting in the forums.