Module builds in Fedora are currently managed by fedpkg. First step is to clone the dist-git repository of your module. For example to clone an existing nodejs module and checkout to the 8 stream, run:
$ fedpkg clone modules/nodejs
$ cd nodejs
$ git checkout 8
A new build is submitted by the following command:
$ fedpkg module-build
Fedpkgs provides other modularity-related subcommands:
$ fedpkg --help
...
module-build Build a module using MBS
module-build-cancel Cancel an MBS module build
module-build-info Show information of an MBS module build
module-build-local Build a module locally using the mbs-manager command
module-build-watch Watch an MBS build
module-overview Shows an overview of MBS builds
...