At first, I bought a top-bar for it, like this:
https://www.amazon.com/Allen-Sports-Tension-Bicycle-Cross-Bar/dp/B000ELSSZE
That only kind of works with my rack.
So, I just ordered one of those that you put the tires into, then drop a bar over the wheels.
https://www.walmart.com/ip/Fultyme-RV-1300-Hitch-Mount-2-Bike-Rack-200-lbs-Capacity/692554514
It's on backorder, so I've not gotten to try it out. But, it sits lower, so easier to pick up to put into the rack, and it shouldn't tear up the paint.