Hi
It’s quite simple but a bit of a science.
First of all you need to make sure that all track rod ens and steering linkages aren’t worn.
So this is how I do it.
Put car on ramp with front wheels on turn plates Apply Park brake and lock steering so it’s straight.
Now put laser on rear wheels facing to the gauges on the front and remember the readings example ( stand at back of car looking forward left wheel 6 and right wheel 8 so there’s a difference of 2 so remember the 2 ) now swap the gauges front to rear. Now set the tracking on the front wheels for example +2 now stand at the front and look back to the rear the rear gauges may have for example once again say 8 left and 4 on the right add the numbers together and you have 12 so now You half the number on each side to 6 and 6 and remember earlier the extra 2 so it’s 2 to the right so now readjust it you take 1 off the left making it 5 and add 1 on the right making it 7 tighten all you lock nuts and you car should steer nice and straight........... but this is how it’s done on modern cars