If the rings came with expanders, they should be used. The ends of the expanders should be butted up against each other, not overlapping, and not aligned with the gap in the oil ring.
I agree with Scottly with one caveat. Occasionally, aftermarket manufacturers provide "universal" replacement parts. I would measure the pistons' oil ring groove depths versus the width of the oil rings with and without the "expanders" to see if they fit properly. I would use them if they fit. They may reduce the oil ring "flutter".
