From this post
https://endless-sphere.com/forums/viewtopic.php?f=3&t=106233&start=25#p1568651
back when I finally got my wheels from BCH, some details about condition, etc (broken parts on the IGHs, etc, because they can't be bothered to pack anything and just throw them in boxes to rattle around and bash against each other, knock holes in the boxes, and let other parts escape during shipping).
You'll need a shifter for this hub, whcih you'll have to locate, and based on what I found at the time and in the months afterward is likely to cost almost as much or even more than the hub itself. Sample link search:
https://www.google.com/shopping/product/11122361215750466890?&biw=1115&bih=987&q=Sturmey-Archer+RX-RD3+shifter&oq=Sturmey-Archer+RX-RD3+shifter&prds=epd:11478549824847428722,prmr:1&sa=X&ved=0ahUKEwjI1Luh3rfpAhUQvZ4KHX7ZAyYQ3q4ECK8L#sellers-grid
That's just the shifter, and doesn't include any of the other bits and bobs you may need depending on what else is missing or broken off the hub by the time you get it from BCH.
I haven't looked in some time now, but I never found one worth buying for the ones I have, so if I ever use them as IGHs and not just drum brakes, I'll have to build a shifter or modify something I already have to have the right cable-pull-stop points.
The parts to make the brake work are easier to locate or make yourself, but they are more things to buy that don't come with it.
It may be cheaper in the long run to buy a new complete IGH wheel (or bare IGH and lace your own if you do that).
It's possible the brakes are already broken in from their use as Jump bikes, but I would bet most people used the front disc brakes instead, based on the wear seen on the rotors of my front motors that came with the sets. If/when I build these into something needing the drum brakes I find the braking is poor, I'll probably just setup a fixture to wear them in, starting the wheel up and engaging the brake, stopping the wheel and repeating over and over until braking force triggers some switch or sensor indicating it's enough for my purposes.