To start with jack up the back wheel ( brake pedal side).
If nothing is siezed up you can tighten up the lever pivot point a bit at a time, while testing the brake by pressing the pedal and turning the back wheel. You can do a bit of adjustment on the operating lever, the back nut should always stay at the end of the rod, the double nuts to the front of the lever can be unlocked and wound toward the operarting lever.
I had to take the brake caliper right off as the 2 push pins were completely siezed up. If you need more help just ask ;)
Regards rog8811