Your razorweld should have come with 2x of the 2 pin plugs. You need to solder those to the leads going into the THC controller and to the torch on/off port. That lead goes from THC unit to your control box and does not need altering.
My 2 pin plugs almost got tossed out when I opened the razorweld… Trapped under flap. They are just plugs, no wires. You have to open ends and do detail solder/shrink-wrap work.