Flex objects with non-quark themes

I’m trying to get the Rana theme up and running with flex objects, but I’m very new to Grav and I seem to be missing something important. I got things working mostly the way I wanted under Quark, but when I tried to copy the work I’d done in the Quark theme over to Rana, none of the flex stuff is working properly.

Can someone point me in the direction of the steps I’d have to take to get flex-objects working with any other theme?