right back home from work will try to explain to you step by step.
click on settings at the top of this page, then click edit sig, on that page you should have from the top preview, then edit sig and at the bottom sig pic.
go down to sig pic at the bottom then option 2 were it says browse click that. once you click that locate your picture then press upload, then press preview sig in the edit sig section then look at the preview above that. it should be okay if so dont forget to save it, any problems write again and will try again all the best. p.s in the edit section your sig might not show up as pic like mine says [sigpic][sigpic] but in preview comes out as a picture.