The first step is to cock the hammer.
Then you need to put a little oil on the safety...
and some light grease on the detent and detent spring.
Insert the safety and the lower from the left side...
and secure the receiver on a hammer block that is held in the vise.
The safety detent goes here:
Insert the safety detent spring in the hole in the pistol grip.
Line the spring up with the hole in the lower and slide the pistol grip into position.
Here's a tip that may save some frustration: Tape the end of the screwdriver with masking tape then force the bit into the screw slot.
This will hold the grip screw, making it easier to install.
Be sure to check the safety several times for proper functioning.