Very carefully! Put stands under the frame before any work is done, and yes you may need to re-stand it a few times until it's where you want it, but once the adjusting lever is disconnected, the car can and will drop to the ground without the stands...turn the switch in the trunk off, remove the adjusting end from it's anchor, and turn it, one way lowers it and the other way raises it...on 92 I think it's tighten to lower, but not possitive!
http://www.lincolnsonline.com/
go here and there are links to air ride sites...