Help with main relay

Well i have to replace my main relay.first of all i wanna know is where its at i think its by the steering wheel where you put your change im not sure.Anyways i wanna know how to replace it for a new one.Please help me out step by step.

Thanks bro.I turned mine to acc2 and i can hear the fuel pump.So i guess thats not the problem.Well my car turns on after like my 3rd atempt so i figured it was the main relay.It kind of stalls and shutts off.I guess its somehing else.