Stand the back of the crib up on its legs. Position it so the front is facing you. Hold the left-side rail up to the back's left side.
Line up the holes in the side rail with the holes in the back. Secure the two pieces together using the provided bolts. Tighten the bolts with the provided Allen wrench. Repeat with the side rail on the right.
Lower the mattress support into the crib's center opening. Lift the four mounting flanges, one in each corner. Line up the flange's hole with one of the height holes in the corner of the crib. The top hole is the highest mattress setting and is recommended for newborns. The bottom hole is the lowest mattress setting and is recommended once the child can pull himself to a standing position.
Insert a bolt through each flange. Tighten the bolts with a hex wrench. Lift the front piece up to the crib's front.
Line up the holes in the front piece with the side rail's holes. Place bolts in each hole and tighten them with the provided hex wrench. Double check that all bolts are tight.