But like how I am supposed to get into the car because in the opsive demo, it asked user to press R, but there is no "R" in vr controller.This idea sounds fun. I'm actually not sure if it will work. In theory the character should stay in the car, but you may need to move the head position manually to keep up with the car moving.
You can change the button mapping by selecting the ability and then changing the input name.
If you got in the car then the ability is working. The SkyCar is taken from Unity's standard assets so you'll likely need to modify it's code a bit in order to work with the VR controllers that you are using.