Did not note how wires were connected when I removed old fixture. Box has 2 different 3 wire cables entering it. Each has a black wire, a black with white stripe wire, and a copper (ground) wire. The 2 coppers have been crimped together and connect to a screw in the box. My new fixture has the usual 1 black, 1 white, and 1 dopper wire. I attached the copper to the other coppers but don't know how the others should go. Tried connecting all blacks together, whites to white stripes... no go. Tried couple of combinations but breaker just trips each time. Breaker is operating fine when I disconnect this fixture. Probably an easy answer to this but I have about zero knowledge. Any suggestions?

First, a cable with two insulated wires and a bare ground wire is not 3-wire cable. It is 2-wire (and that really should be 2 conductor) cable with a ground. As you can see the correct terminology is conductor not wire and the ground is not a conductor.

Next where are you located? In US the hot is black in a 2-wire cable and the neutral is white. If where you are located the hot is black and the neutral is black with white stripe, the following applies. But only if black is hot and black with white stripe is neutral.

The black in one of the 2-wire cables in the ceiling will be hot.
You can determine which cable has the hot wire by checking for voltage between the black and the ground. The neutral of that cable (black with white stripe) gets connected to the white of the light fixture. The hot black gets connected to one of the wires in the other cable. Right now you don't know which one. You will have to remove the switches and look. One switch will have the 2-wire cable from the ceiling and a true 3-wire cable (4 wires, 3 conductors and a ground). The other switch will have only the 3-wire cable. At the switch that has the 2-wire cable from the ceiling and the 3-wire cable going to the other switch, one of the wires in the 2-wire cable will be connected to the switch. The other wire in the 2-wire cable will be connected to a wire in the 3-wire cable.

Back to the ceiling. Connect the hot black to the wire that is connected to the switch. The other wire in that cable is connected to the black of the light fixture.