You can add users as collaborators to your personal repository.

Repositories owned by an organization can grant more granular access. For more information, see "What are the different access permissions?"

  1. Ask for the username of the person you're inviting as a collaborator.
  2. On GitHub Enterprise, navigate to the main page of the repository.

  3. In the repository's right sidebar, click Settings. Repository settings button

  4. In the left sidebar, click Collaborators. Repository settings sidebar with Collaborators highlighted

  5. Under "Collaborators", start typing the collaborator's username.
  6. Select the collaborator's username from the drop-down menu. Collaborator list drop-down menu
  7. Click Add collaborator. Add button

Further reading