If your community is set to Public, users can register to join your community and benefit from the offerings in your community. Under your community's general settings, set the Community Access to Public:
Once you've done this, users can register to join your community via the community landing page (https://<your-community>.disco.co).
A few aspects of the registration page can be customized by going to the Admin Dashboard > Settings > Registration.
And this is what the registration page looks like: