Refer to your instructions. This can be fiddly, so build the unit outside the cabinet first so you know how it fits together. Take it apart and reassemble inside the cabinet. Place the base of the centre pole into the bottom bracket. Extend the pole and place it into the top bracket and secure in place.
The locating holes on the pole allow you to adjust your baskets to the right height. To position the middle basket push the fixing pin through the pole at the desired height. Slide the mounting cap down and rotate to lock. Rest the basket on top. Secure the fixing clip on top of the basket. Position the lower basket and place the fixing clip on top to secure it in place.