I feel like the biggest moron, I can find the profile pic setting, but not my  signature. XD (Want to add one)

Hover your mouse over your avatar in the top right of the screen and in the drop down box choose "Settings".

Next click on the "biography" tab and scroll to the bottom.

Go to settings and then biography .. after scroll all the way down and you'll see a box for the sig.

And don't feel bad. It took me a while to find out as well.

Settings/Biography

Hover over dat X mecha in the top right of the screen,
Go to settings,
Go to biography,
Scroll down to signature.

Thanks guys. What's the sig image size limit?

Is 360x640 too big? Finding it hard to find decent images smaller

According to Yo_John who wrote on my wall

"I changed the size of your sig since it was far too big (max sig length is 270 pixels tall)."

3 years on this site and you don't know how to make a sig? >_>

"Biography" didn't seem like the logical place to look.