There's a bit more to installing spacers than yanking the wheels off and sandwiching them between the wheels. Here's how to determine what kit is needed.
The outermost point of your tire/wheel combo will be at the outermost "bulge" of your tire's sidewall. Using a straightedge or ruler flush with both the top and bottom of the tire - measure the clearance from the outer face of the tire to the inner lip of your fender and record the results onto paper for later.
In this picture, we can gauge the clearance using a tape measure (straightedge not shown):
Next, begin by jacking up the vehicle and securing with jackstands. Remove wheel and clean hub of all dirt and/or surface rush with a wire wheel to ensure a clean and flush mounting surface, eliminating the chance of vibration:
A small amount of anti-sieze on the hub lip will make spacer removal easier if needed:
Macht Schnell spacer mounted to front wheel, ready for wheel mounting:
Extended lugs must be used and are included with all Macht Schnell spacer kits. Secure wheel with new fasteners and torque to 85-90ft lbs, reinspecting after 50 miles.