Make sure the truck is on the ground and at ride height before proceeding. Using a 1/4" drill bit, drill the Coupler Lock holes through the pilot hole in the rear bar section. Drill each hole from the outside in and not in one shot to be sure the holes line up with the coupler. It is critical to get these holes drilled in a precise manner. Next, use a 3/8" drill bit to open the holes up. Then, use a 1/2" bit to open the holes up once again. Make sure all holes are drilled from the outside in. Finally, use a 5/8" drill bit to ONLY open the OUTSIDE hole. The INSIDE hole must be 1/2".
If you have to take the bar off the truck to drill due to lack of clearance, you can do this. Drill the 1/4" outside hole and sharpie the small tube where it meets the big tube. Also, measure the bar length. When the bar is off, put a drill bit in the hole you already drilled before moving to drill the other side.