Use the Allen wrench included in your package to remove the screw at the bottom of the pole. If you did not receive an Allen wrench, then any wrench or pliers would suffice (you might need to use some force).
Insert the dress form's pole through the top of the base and use the Allen wrench (or pliers) to secure it in place.
There are two different models in the tabletop dressform category. One has its connector in the center and the other has it on the left side. The latter model can be fitted with pants/ trousers.
Note: while connecting the model with its hole on the left side, it would be best to push as much of the pole through the hole as possible. Fastening the side hole to the very top of the pole will cause the dress form to lean to the other side.
The height of the dress form can be adjusted by raising and then tightening the top pole.