Reese has great instructions too if that is what you have. Here are the key factors IMO. First, the ball height on your truck is key. It should be about 1 inch higher than the top of the inside of your trailer coupler when the trailer is level. This assumes your truck will drop about 1 inch when hooked to the trailer. Then your WD bars should be adjusted to the point where your trailer is level; and your truck drops the same amount (about 1 inch) at both the front and rear. That's kind of the "Cliff's Notes" version!
But make sure to read your manufacturer instructions!! They might vary from what I just said and should be your primary source of information.
2012 F150 FX4 Ecoboost, 2016 Surveyor 274BHS
2003 Yamaha FJR1300, Demco Premiere Slider
1969 John Deere 1020, 1940 Ford 9N, 1948 Ford 8N
Jonsered 535, Can of WD-40, Duct Tape
Red Green coffee mugs