1. Separate your upper and lower receivers.
2. Remove your buffer and spring from your existing set-up.
3. Loosen the stock's castle nut with a telestock wrench.
4. Reach into the back of the lower receiver and depress the buffer retainer while unscrewing the stock. That way it won't go shooting out. Also make sure that you don't lose the takedown pin's detent and spring which are sandwiched between the stock's plate and the lower receiver.
5. Screw the new stock onto the lower receiver while depressing the buffer retainer. Make sure that the takedown pin's detent and spring are installed and be careful not to bend the spring over between the stock and lower receiver, as this will crush it.
6. Thread the new stock into the lower receiver until it overlaps the buffer retainer. This is what holds the buffer retainer in place.
7. After you've overlapped the buffer retainer, check to make sure that the stock is plum with the rifle. If it is rotated a little too far and is crooked, loosen it slightly to plum it up. Just don't uncover the buffer retainer completely.
8. Tighten the castle nut.
9. Install your new buffer spring and buffer. Do NOT use your old buffer and spring, as they are NOT compatible.
10. Put your upper back on your lower, and go shoot that thing!