1. The shelf has two screws installed at each end.  Position the brackets with their fingers facing away from the rounded edge of the shelf and the bent over bracket parts facing each other as illustrated below. Lower the bracket over the heads of the screws and slide the bracket toward the front of the shelf.  Tighten the screws.

2. Two people are needed to slide the fingers into the slots on the uprights.

3. Tap the shelf top near the uprights to slip the fingers down into position.  It doesn't take much of a tap, and can be done with a closed hand.