Place the base of one Lazy Susan insert in the center of the lower corner cabinet. The inserts are the polelike pieces; the base of each is the flat end that contains the screw holes. The bottom insert is slightly smaller, or has a smaller diameter than the top.
Line the center of one shelf over the pole insert, and push the shelf down the pole. Repeat the step to put on the second shelf.
Push the top insert into the bottom insert. The top insert is also a pole with a slightly smaller diameter.
Push the second shelf up along the insert, hold it in place with your hand, then place one of the plastic couplings underneath the second shelf, and around the outer diameter of the insert, to hold the second shelf in the up position.
Push the first shelf up as well, but keep it several inches below the second shelf. Place a coupling below it to hold it in place.
Verify that the Lazy Susan can properly turn in the position that it is in when the cabinet is open, and the lower cabinet door can close with the Lazy Susan inside. Also extend the top insert and make sure it lines up with one of the braces at the top of the cabinet.
Drill screws into the mount holes in the bottom of the insert to the floor of the cabinet.
Extend the top insert up so its mount holes align with the wood brace at the top of the cabinet. Then insert screws through the top insert's mount holes with an electric drill.