I found this presentation's instructions helpful: OpenStack&NSX-T - Network Topologies Configuration Guide
Starts on page 57.
BTW, this assumes you want to apply default RBAC and allow all projects to connect to the network. You can not change it later. If you think you may ever want to disallow this network from a project, the alternative is to enable explicit RBAC. In this mode you will need to assign the network to each project that needs it. https://docs.openstack.org/neutron/pike/admin/config-rbac.html