starter solenoid?

alrite so i just bought a 1978 ford bronco custom for $500...me and my friend are tryin to fix it up. one day my friend accidently put the battery cables on backwards and i believe it shorted out something. whenever i try to start it nothing happens except for the lights turning on...no click no nothing. when we tried to start it with a pair of channel locks on the starter, it tries but wont fire? What is the problem?

Check the fuse able links. They are down by the starter. If burned use wire two wire sizes smaller than the bigger wire. Or go to a scrap yard and buy a new section the same color.