install Postgresql and create a user+schema for maas
install your maas region controller : maas init region --database-uri "postgres://<maas_db_user>:<maas_db_pass>@<PGSQL_DB>/<maas_db_schema>"
connect to maas and from there, go to the controller tab then add new controller, you’ll get a command line including a token to use in order to register your rackd controllers
That’s about all you need to do.
You can also very easily add more region server (at least one more) which will let you enable HA on the DHCP/PXE side.
Warning : be extremely careful to have all your machines in sync with NTP or you might encounter lots of troubles.