Solder the first lead of C1 into the circuit board, from the 2nd lead on C1 bend/twist it to the side of the board. Take a wire from lead 2 and go to a 500k audio taper pot. Connect into terminal 1, put a jumper from 1 to 2, go 3 back into where lead 2 of C1 would normally be.
For the existing pot terminals on the circuit board jump terminal 1 straight to terminal 2 or 3 which is ground. Everything should be good from here, NO CRACKLE and better range!