I was wondering, how can I put in a 5th or 6th cell? I was at radio shack and the guys were saying it'd jsut burn the engine, what a load of

So, what whould I need to do to get it on and power? Soder gun or something? I tried to install one myself but then my dad pointed out something about soddering. Can someone like draw up a diagram on the installation of a 5th cell? I wanna show my friends what's what one day when i come by and smoke them.