Pull up on the backside of the seat hinge covers, swinging them open. Press the plastic inserts with the bolts' holes in them into the openings in the hinges so the inserts click into place.
Insert the seat’s bolts through the holes in the plastic inserts. Lower the toilet seat onto the toilet bowl, threading the bolts through the holes in the back of the bowl.
Put a flat head screwdriver’s blade into the slot on top of one of the seat’s bolts, holding the bolt stationary. Use your other hand to press the plastic nut piece onto the end of the bolt on the underside of the toilet’s bowl, so it fits firmly on the bolt.
Turn the bolt with the screwdriver clockwise until it's tight and the toilet seat doesn't shift on the toilet. Repeat the process with the other bolt. Snap the hinge covers in place when both bolts are secured.