How do you position the OVRCharacter controller to touch bottom to Grond ?

I drag the OVRCharacter controller and it's either above the ground or in the middle of it . I don't understand why. Doesn't it have a collider? ........Oh would it help if i put a collider on my plane/floor? but i tried a scene with rigidgoby objects and they didn't fall through. so the plane must have a collider already.  Anyways any help appreciated