This is how it appears on my control panel, i dont remember there being any restrictions on signature editing in the past but this site is new so if you dont have the option let Massamo know as per above.
Update: when using the URL provided by MASSAMO, I got a message stating that I had to have 10 posts before the signature feature would be accessible. SasaPinjic was right, so now we know how this is the way to get to it.
More posts, here I come.