Add users without registration allowed

Hello,
On a self hosted instance of bitwarden, I have disabled user registration.
Is there a way to add users manually or through an invitation link? In the administration panel, the users section is read-only and the documentation does not explain anything about it.

Tnx,

Hey there, so the invitation section is greyed out? Do you have an active organization?

Thank you!
I thought that the user must be registered in the instance before being added to the organization.