Unscrew the black locking screw and push the plastic cover round to where you can access the metal pins that fit in to the degree 'teeth'. Lift up the pin and slide it to the desired degree of flexion. Do this on both sides of the brace, slide the plastic cover back in place screw the locking screw back in to place. Don't worry about the extension side. For us QTRs it's all about flexion. Here's a couple pics I hope will help.
So you can see in the top pic the locking screw is out, cover open and pin is at 90 deg. Bottom pic is all locked up again and ready to put brace back on.
Follow up with my OS this week. Still no PT or strength or ROM work for me yet. Walking pretty freely now though, but can feel the scar tissue restraining my ROM and keeping things tight. Light stretching and leg lifts in bed with extension from a chair are a breeze now. Hope I get the green light for PT rehab this week. Best to all.