Wheel, simulator help
 

Purchased a set of simulators/wheel covers for my '70 1 to. 3 piece, wheel center cap and ring that goes over lugs and snaps on to center cap, am I stupid or should some washers have come w/set to hold center ring on, which would keep wheel cover on behind it and allow center cap to attatch to it or is that something I needed to pick up ? Thanks in advance. Came UPS.