The video below applies to the Celestron Skymaster 15×70, 25×70, 20×80 binoculars plus the Cometron 12×70. Collimation is a very simple process with no dismantling needed. The adjustment screw is located under the rubber covering on the hand grips. I like to work on one side only. Only adjust the opposite side for minor adjustments if needed.
Place the binoculars on a solid base or tripod to do this. Invite a friend to help if you struggle to make the adjustment while looking through them at the same time. See the video below for more details.