The drawer must be installed on a fixed shelf, otherwise the shelf will tip up when the drawer is extended. To secure the shelf fasten a steel angle to the back of the shelf and the back of the cabinet.

Place the drawer in the base.

Place the drawer base on the shelf.
Center the base and set it back 1.5" from the front of the shelf.
Screw down the front 2 screws followed by the back screws.