1)Make sure the servo is in the car in the exact same place you plan to run it (some cars let you adjust the servo location)
2)Remove all steering linkage from the sevo
3)Set the steering trim tabs on the car to dead center
4)With the radio on and a battery hooked up to the car so power is getting to the servo, NOW connect the servo saver on the servo getting it as close to center as possible
5)Adjust the trim on the radio to get it perfect
I like my trim to be as close to dead center as possible so that way I have adjustment either left or right if I ever need it during a race.
You are always better off spending the extra time setting up the steering with a mic and a setup station than you are trying to get the steering right on the track. Actually get it right on the bench first so you only have to make micro changes, if any, on the track.
Always set the steering up with the radio on and power going to the servo...Measure, then remeasure, put it on a setup station and measure it again. Do this as many times as you need to make it right. Once it is done right, you will very rarley have to fuss with it again unless the car needs major surgery.
Remember you may also have to adjust the length of the link that connects the servo saver to the bell crank to help get the trim tab closer to center.
Most directions for kits give you the length that each tie rod in the kit should be. I find for perfect steering that these supplied lengths are closer to starting points or suggestions to get you "in the ballpark" than they are actual specifications.