Cock.

Using the included screwdriver, unscrew the screw on top of the drum.

Place the cartridges in the drum so that the pins fall into the slots provided for them.

Install the drum in place by carefully tightening the screw with a screwdriver.

Move the small semi-circular lever that is on the opposite side of the firing pin. This is the trigger.

Kindly look at the video of the Ring-Gun in action