Once your videos are loaded, click on button ‘A’ to the right of the video slider (scrubber). Now move video A to a key point in the action.
Repeat with the steps above video B.
Now press the AB button to lock them together. Remember they can only be in synch at the 2 points you chose.
If you play the video, events later in the video may be out of synch if the action is happening at different rates.