How can I grab an object (cube) with hand tracking?

Hi, I am setting up the hand tracking and not the controller.  I added OVRGrabber to OVRHandPrefab and I have Sphere Collider, and Rigidbody. I also added OVRGrababble in the Cube. I can move around the cube with the hand but I cannot grab the cube. How can I grab an object? Is there any good tutorial for this? Thank you!