The light box works. There was a light up there, and no, I’m an idiot and I did not check how it was installed when I took it down.
Instead of a black wire and a white wire like the manual says, I’ve got four black wires and two white wires. It’s an old fixture. There are three areas or circles up in the ceiling. One has a black wire and a white wire coming out of it, another one has a black wire and a white wire coming out of it, and the third has two black wires coming out of it.
I don’t understand what to do. Do you twist the two white wires together to make one white wire? And what about the four black wires? Do I twist the two together coming out of the same hole or the two that are coming out of different holes–or some combination of all of them?
I understand apparently one or more of the black wires might be grounding wires but they all look exactly alike–black wiring cover with a white strip down the middle.
Can anyone help with my possibly confusing question? Thanks.

you messed up by not looking at how they were attached but this is the old stile of wiring where the power goes straight to the fixture and then a wire goes off to the switch. You need to try and see how the other light was set up because it sounds like you have too many wires. Some of them may have been taped up if so they need to be re-taped and left alone. It might be best to get a tester and test the wires and see where the power is coming in and go form there.
It sounds like you have an inbound circuit, and outbound circuit and a set of switch leads. If so (AND IF YOU CANT TEST TO BE SURE, HIRE AN ELECTICIAN!), you would connect one of the two black wires that come from the same hole to the light fixture black wire. Hook ALL of the white wires, including the one from the light fixture together and hook all of the black wires together except the one you hooked to the light fixture, including the “extra” one from the switch.
Test with a VOM meter before you start. If I am right, the two black wires from one hole will have no voltage whether the switch is on or off. They will show continuity with the switch on and none when it is off. One (and only one) of the black wires will have voltage on it whenever the breaker is on and all the other wires will have none whether the breaker is on or off. The black/white pair with the hot lead is your inbound (feed). The other black/white pair is feeding another load such as outlets or other lamps. The double black pair goes to the light switch on the wall. If you do not have a VOM or if you are not sure how to use it to check the circuits CALL AN ELECTRICIAN!
Bert