Your seat height is adjustable using the hexagon socket screws on the clamp under your seat.
Loosen the screws with the hex wrench, insert your seat post past the minimum insertion line marked on the post. Adjust your seat to your desired height, and then tighten the socket screws on the clamp to lock your seat in place. Make sure your seat feels stable after you attach it.
Adjust the seat to your preferred angle by loosening the nuts that attach the seat to the seat post. Ensure the nuts are tightened firmly and that the seat does not tilt forward or backward while you’re sitting on it.