Your seat height is adjusted by a quick release. Pull the quick release lever. Insert your seat post past the minimum insertion line marked on the post. This ensures that the seat lock has a secure grip on your seat post. Adjust the seat to your desired height, and then tighten the adjusting nut on the quick release lever, then push the quick release lever closed to lock your seat in place. Ensure you do not over-tighten the adjusting nut by the quick release lever. Make sure your seat feels stable after you attach it.
Adjust the seat angle to your preferred comfort by loosening the nuts that attach the seat to the seat rail. Ensure that the nuts are tightened firmly and that the seat does not move forward or back while you're sitting on it.