do the same to the patch cable if it has rubber sheleding just strip off about 0.25"

to find the right wires (color codes are different depending on the manufacturer):

take a multimeter and set it to resistance (or contanuity if you have a fancy one)

put one probe on the sleeve(the biggest part of of the 3.5 mm plug (the ground) and try each wire in turn with the other probe to find it

next repeat the process with the tip of the plug (the left channel)

the last wire (if you have 3) will be the right channel

you may have a 4th wire this is a seccond ground wire