You got a very good deal. The Knight Bighorn is an excellent rifle. If your model has the 22" barrel and #11 percussion cap ignition that's still a good deal. Start out trying something simple. 85 grains of powder and a 240 grain XTP will normally shoot very well out of the rifle. Another thing you might try is some of the shockwaves. I shoot a Wolverine LK-II and it shoots Shockwaves excellent with 100 grains of powder.

Actually I think you are going to find that about anything you put down the barrel will normally shoot real well.