The brakes are adjusted by shortening or lengthening the threaded rods that connect the peddle to the lever on the brake. There is one on each side just under the foot platform.
You should just be able to remove your brake linkage and unbolt the round cover that holds the pads, etc. Then pry the cover off (the pads will come off with it). You should be able to tell what is wrong. Hopefully you will be able to fix it by adjusting the rod.