No picture, on step through frame, a woman's bike, go under the seat stay/chain stay/seat tube joint, which is under the saddle, and under the upper down tube. This works on most, but not all, step through frames, as my wife's Trek Sole Ride requires an adapter to load.
If it is a traditional diamond frame, a men's frame, just hang the top tube on the rack.
As for a rack recommendation, any bike rack that uses two arms to hold the bikes will hold any bike, but some may need an adapter. The racks that rely on a single clamp to hold the top tube won't hold a step though frame without and adapter.