The adjustable front axle chassis have holes in the top of the axle hoop and the bottom of the chassis that will accept grub screws. The lower holes are somewhat inboard of the axle hoops.
The adjustment screws are the same diameter as wheel grub screws. Wheel grub screws can be used for the top screw but longer ones are required for the bottom. The best screws to use are the ones from Slot Car Corner; they have an oval head. The available Slot.it screws will work fine, though. With these screws, the axle height can be precisely adjusted to get the front tires just barely off the track surface.
This setup is one of the minor tweaks that will produce smoother running and slightly faster lap times but will still not result in as much difference as familiarity with the track and getting in more practice laps.
Good Luck!