swap t0 for t2

Hi, my t0 input on RAMPS appears to be broken, as it reads 50C even without a thermistor plugged in. Could someone tell me how to use t2 in place of t0 for the hotend thermistor? I believe some changes are needed in pins.h in marlin but I have never made changes there before and would rather someone more experienced guided me through it.

Thanks,
Adam