Get Used to Your Kneeling Chair
Your bottom should still be carrying the bulk of your weight, and the knee pad is there to act as a support for your shins.
Begin by sitting, bottom first, on your seat first and then moving into the kneeling position afterwards. Even after you have placed your shins on the kneepads, the bulk of your weight should be on your bottom. Returning to Peter Opsvik's concept of variation and movement, it's important to vary your seating position frequently during the day.
Allow a week or two to get used to it
It may feel awkward sitting in this new position at first if you have been sitting mainly on traditional chairs before. Your body will need time to adapt to its new open posture seating position as your muscles and bones that have gotten used to a particular seating position. It may be a good idea to try some regular exercises to rebuild your strength.
Sit down Move on
When Peter Opsvik designed the original Balans kneeling chair over 30 years ago, movement and variation were very much what he had in mind. He recognised that sitting in the same static position for long periods of time is bad for your health and this hasn't changed. So keep changing position regularly, as the Balans chairs were designed for it.