All of the answers so far have been correct in that you simply inflate them until the truck rides well. Your actual pressue will depend on what type of bag you installed and quite a few other variables. Personally, I would start by inflating them until the truck is lifted back to about an inch lower than it was when you started. I feel sure that the weights you gave for the trailer are empty and that you will add both total weight and tongue weight as you load up for a trip. I would not get too excited about tongue weight until after it has been loaded and then checked. Also, just to be clear, the air bags are rated for an air pressue of 100 pounds per square inch, not 100 pounds on them.
I feel that a truck empty is at its maximum designed ride height and is at its minimum designed ride height with a full rated load. So somewhere in the to middle should be a good place for driving around and for the headlights to be well aimed. You will probably find a sticker on the hitch that tells you to use a weight distributing hitch if your trailer weighs over 5,000lbs(loaded) or your tongue weight is over 500lbs(loaded) and yours probably will be as jmtandem pointed out. The weight distributing hitch does a lot to reduce bouncing of the rear end of the truck while towing.
Finally, most people end up filling the bed of the truck with stuff when they go camping. The air bags are really more for helping with that weight than they are for the tongue weight. The equalizer hitch should handle a large portion of the tongue weight.
