First identify the cable that has the constant 'hot' wire using a volt tester. (If you don't know what a volt tester is or how to use it then you should call an electrician). Next take the light fixture down & verify that all of the wires are connected like color to like color. If this is not the case, call an electrician as I am not comfortable with trying to explain that one hear. Otherwise reinstall the light and then..... Once you've identified the cable with the 'hot' wire then you need to identify which wire controls the light. You can do that simply by touching the 'hot' wire, (black in color) to each of the remaining black wires, one at a time until the light comes on, this is the 'switch leg'. The 'switch leg' connects to one of the terminals on a single pole switch, (doesn't matter which one). All of the other black wires should connect together, with a wire nut, with one extra wire that you add. This extra wire connects to the other terminal on the single pole switch. All the white wires should connect together & all of the bare wires connect together. Like to like.
Hope this helps.
Hope this helps.