1. Place the bolt/carrier group in the rifle and close and install the pins.
2. Push the charging handle all the way to muzzle end of the rifle.
3. Install the Op-Rod with the roll-pin pointed in the direction of the front sight post - straight-up.
4. Push the Op-Rod into the action (compressing the spring) past the point that the roll-pin engages the charging handle and then rotate it 90* clock-wise.
5. Pull-on the Charging Handle to see if you have correctly engaged the roll-pin into the Charging Handle by pulling the Charging Handle to the rear SLIGHTLY but do not let it snap forward under spring pressure.
6. Push the Bolt Carrier to the muzzle end of the rifle and with a plastic pointed object, depress the Op-Rod engagement button and force the Bolt Carrier towards the muzzle until it stops.
7. Move your plastic pointed object to the shallow depth cut in the Bolt Carrier group to just above and the the rear of the Op-Rod engagement button and push it toward the muzzle-end of the rifle.
8. Twist the Gas Piston Head back and forth while pressing it-in toward the butt-end (clockwise and counter clockwise until the Op-Rod engagement button pops out towards you) - at this point it should be fully engaged in the Op-Rod.
Good luck - it isn't that difficult.