Old light fixture has 3 sets of black, white and copper. It keeps tripping breaker when installed. Not sure what to do
one of those white wires goes to the switch
one of those black wires comes from the switch
You need to figure out which is which and connect the white wire goes to to the switch to the black wires (this white wire should have black paint or tape on it)
connect the black wire that comes from the switch to the lamp, and (using a short piece of wire) connect the other white wires to the other lamp terminal.