Do you know if your site is hosted by us (Discourse)? If so, we can give you private support. You’ll find the email address for our support team near the top of your site’s admin dashboard.
If your site is not hosted by Discourse, can you share some more details about what you are trying to do? It sounds to me like what you might want to do is send invitations to your forum to a list of email addresses. If so, you can find details about sending invites in this topic: Configure how users can create and send invites for others to join your community.