actually here is picture, the arrow on left is under camper and the arrow on right is where coupler is
You have the two main I-beams. Those should be level front to back. That should keep the weight on the trailer axles roughly equal. (make sure you are checking on a level parking lot).
The bottom of the box beams for the a-frame at the front are obviously not going to match the back of the trailer. Once you get the trailer level, then measure the height of the trailer coupler (to the top oft eh socket for the ball. Before adjusting the ball, check how much the truck squats when loaded. It will probably go down an inch or so, so when setting the ball height for level, raise the ball the same amount as the squat you measured. That way wen it squats, the trailer will be back to level.
If you are off by an inch, not a big deal but you do want it close.
