Empty the contents of the desk drawer onto the desk or onto a countertop. The desk drawer should be empty; otherwise, something could accidentally fall into the drawer recess and obstruct the drawer from closing all the way.
Line up the rails on the outside of the drawer box with the rails in the recess in the desk where the drawer slides in and out.
Hold the drawer at a 30 degree upward angle. Push the back of the drawer into the front of the recess, snapping the rollers into the railing system inside the desk drawer recess.
Push the drawer into the recess, allowing each roller to snap into the railing system in the desk. Close the drawer all the way to ensure it is properly installed.
Open the desk drawer and fill it with the contents you emptied out of the drawer box earlier.