Garlin,
As with arrow saws of all makes, the slot in the rest is for adjusting depth of cut. You only need to have the depth a little past the inside wall of the arrow shaft. Tighten the rest once your adjustment is done - with motor unplugged while setting up.
When ready to cut, I set the nock end in first, then move the shaft across the rest into the spinning cutting wheel. Rotate the shaft opposite to the cutting wheel rotation in a smooth, fairly quick motion. Remove your shaft, prep and install inserts. You will love it. Wear a filter mask if cutting carbons.
Jerry's suggestions for the fence alignment square to the cutting wheel is critical as is getting your fence distance for consistency. Have fun!
Ray