What happens next?

How to set up a race car in the shop before racing
Weigh the vehicle.
Set it to the proper racing weight including all fluids such as fuel, coolant and oil (this weight is usually the minimum weight required by your home track).
Determine the tire stagger to be used.
Install a set of tires that will give you this setting with the proper air pressure in the tires. ( don't overinflate or under inflate a tire to obtain proper stagger.