Connect your scope to the current you want to test by putting the black lead on the ground terminal for the battery and the red lead on the wire for signal return.
Establish divisions for your graph lines on the screen. You may want each vertical line to stand for 500 millivolts or 5 volts, depending on the test in question and the revolutions per minute.
Set your time divisions for the horizontal axis. This could vary from a millisecond to 100 milliseconds, or even more, and will also vary with RPM and application.
Place the ground indicator somewhere near the center of your screen. Generally it will go in the middle, but for applications where you're expecting it to vary more widely in one direction than the other, you can offset the indicator.
Decide on a trigger voltage level and input that into the scope so it knows when to start tracking. Have the sweep run on "recurrent," and once you have a consistent pattern you can freeze it or have the scope continue to monitor without changes.