Create a VM or an LXC container. In this case, I will use a Debian LXC.
Install docker: https://docs.docker.com/engine/install/debian/
Install portainer: https://docs.portainer.io/start/install-ce/server/docker/linux
Or just use the docker LXC: https://community-scripts.github.io/ProxmoxVE/scripts?id=docker