The profile picture is the one that shows in your profile. The avatar is the one that shows next to your name in posts. The Signature text is where you can add BBcode generated by banner code. Once you have 15 posts (which you do) and at least an hour's wait, you get Edit Signature in the Settings. Some other people's banners, when clicked on, will take you to where you can make one like that.
Tips -
Do not buy a supermini nor M402/M401 or you will be buying another ecig within weeks
Buy manual batteries for ease in getting a good hit and for batteries safer from being killed or damaged by juice leaks. We refill everything with eliquid.
If you are a hot heavy dragger full strength smoker, you may want to skip slim ecigs
KNOW what you are buying. BEWARE the seedy upper crust of ecig sellers - there are a lot of ripoffs, a lot of junk or incompatible models, a lot of lies to sell their product above all others. We usually buy at good-priced multi-brand vendors who sell them as their original model numbers/name (like Liberty-Flights.com and LiteCigUSA.net) or from a small number of reasonably priced full line rebranders like Vapor4Life and SmokelessImage for KR808D-1.