I'll keep this short and sweet Wilfy
Knee bars should be right under your kneecap, fine tune it to what feels best for you. An inch here or an inch there made a big difference to me.
Protect the springs with tape. Hockey tape, electrical tape, duck tape. Do a search for tape and you'll find alsorts of posts on here. Chuck on a few layers for good measure.
The hurting of the knees will stop. It's just you're legs getting used to something rubbing against the skin down there. Try some skating knee pads as this gives a more snug fit around the knee area.
And hey, welcome to the forums and how about posting an intro about yourself in the Introductions topic I started.
