First we will add a small cursor to the middle of the screen, to indicate where the center of the car's tire is:

1. In Hierarchy, select AR Prompt and create UI | Image; name it Center Cursor.
2. Set its Source Image sprite (by clicking the little doughnut icon) to Knob.
3. Change its Scale to 0.2, 0.2, 0.2.

If you press Play, I think you'll agree that's helpful.