As an owner/administrator of a community you can invite your members to join during the creation of a new community, or using the invite button found in the community header.
During community setup
In the create community panel you'll see the invite sections. Simply add your members email addresses separated by commas, spaces or semicolons. Once you create the community your added members will receive an invite via email.
Invite button
Look for the invite button in the community header, which you can find at the top of any community page. The invite feature is only visible to community owners/admins. Simply add your members email addresses separated by commas, spaces or semicolons. Once you create the community your added members will receive an invite via email.
You can also share and promote your community, simply copy a share link to clipboard and use as you please, or create a post on Facebook, Linkedin, X (formally Twitter) using the actions at the bottom of this dialogue.