do as mike said...insert the stock into the receiver fully. then, locate your holes using the existing holes in the trear trunnion tang as a guide.

holding your drill bit along side the stock's wrist, apply masking tape to the drill bit as a visual depth guide.

start with a 5/32" bit and keep opening up the hole bu 1/64th" increments untill the screw threads into the stock about halfway without undo torquing on the screwdriver.

for final installation you may want to lube the screw up with ordinary bar soap.

good job!

the ak is a great piece to sharpen one's mechanical skills on.