From the pics you posted, I noticed that you have the 5K weight carrying hitch, not the 7500# weight distributing hitch. The item you are having a problem with is the ball mount, not the hitch, and it will NOT increase your towing capacity. It may have come from a weight distributing hitch setup on another vehicle, but it will not change your hitch to a weight distributing one. In order to get a weight distributing tow setup, you will have to replace the existing rear hitch (the receiver you plug the ball mount into) with a weight distributing unit. If you attempt to hang a weight distributing ball mount with the compensating bars and chains or cam setup on the existing receiver and haul a heavier trailer, it may twist the rear frame cross member.
I just recently upgraded my hitch to a WD model from Valley. It works great, but the install is a bit of a chore. Removing the old oem receiver requires you to remove the rear bumper to get at all the mounting bolts.