I have a single sink in my bathroom at this point, am trying to put a double sink counter top on it. My question is if I have to put a double drain pipes or if I can put a T on the excisting one, same question for the hot, and cold water. Am just worried about the drain pipe hopefully you guys can answer my questions thank you very much guys.

my question is if i have to put a double drain pipes or if i can put a T on the excisting one, same question for the hot, and cold water
You may connect the two tubs to one trap using a continuous waste,(see image). As for the water, simply swap your present angle stops for 1/2X1/4X1/4" angle stops,(see image) and pipe both supplies from there. To change out the stops, shut the water off and remove the old stops. Leave the 1/2" compression nut and ferrule and install the new angle stops using the old nuts. Simple, Huh? Good luck, Tom