Always try the easiest fix first, which would be use a pair of vise grips to remove the broken off stud. If the piece that the points thread into is removable, you might be able to get to the stud from the other side but I'm not familiar with this set-up. You can also try using a punch or small chisel & using a hammer, work the broken stud out. Depending on the hardness of the metal, you can try hammering a sharp phillips screwdriver into the end. If there's not enough metal to grip, try an easy out. Use the biggest one that will fit.
If an easy fix won't work, you'll have to drill out the stud & either rethread or heli coil the buggered up threads.
If an easy fix won't work, you'll have to drill out the stud & either rethread or heli coil the buggered up threads.