Since this page is apparently the top result on google, Heres a link to how to do it.
https://martingladdish.co.uk/technology/setting-up-docker-under-qubesos/
That page has more detail, but here are the instructions in case its down.
- Install docker engine, following the instruction on https://www.docker.com. NOT DESKTOP as that wont work in Qubes (unless you enable nested virtualization)