Rear sway bar mounting ?

You bought one of the better sway bar kits. This one has a bracket that is welded or bolted to the axle then brackets that bolt to both sides of the frame rail. All you have to do is mount the bar on the axle first, center the axle brackets,get it level with the car then mount the frame bracket to the bar first, move up the bar to the frame keeping it level and the mounts straight. you want the axle links to be plum. then mark your holes on the frame rail. dont use a jack under the car body as you want the car to sit normal on the suspension, if you must get it up a little use stands under the axle. To make it easy use a clamp on the frame brackets to hold it up and then you can get it level and straight.
If you have a real good sway bar then it will have adjustable links on the axle side to adjust the feel you want.