Adding outside collaborators to repositories in your organization
An outside collaborator is a person who isn't explicitly a member of your organization, but who has Read, Write, or Admin permissions to one or more repositories in your organization.
Only members with owner privileges for an organization or admin privileges for a repository can add outside collaborators to a repository, unless an organization owner has restricted the ability to invite collaborators. For more information, see "Setting permissions for adding outside collaborators."
If your organization requires members and outside collaborators to use two-factor authentication, they must enable two-factor authentication before they can accept your invitation to collaborate on an organization repository.
When you add an outside collaborator to a repository, you'll also need to add them to any forks of the repository you'd like them to access.
On GitHub Enterprise, navigate to the main page of the repository.
Under your repository name, click Settings.
In the left sidebar, click Collaborators & teams.
Under "Collaborators", type the name of the person you'd like to give access to the repository, then click Add collaborator.
Next to the new collaborator's name, choose the appropriate permission level: Write, Read, or Admin.