If you have administrative access, you can convert your public repositories to private ones.

  1. Open the repository's page on your GitHub Enterprise instance.
  2. Settings tabClick Settings.
  3. Make Private buttonClick Make private.
  4. Warnings popupRead the warnings.
  5. Type the name of the repository that you want to make private.
  6. Warning PopupClick I understand, make this repository private.

Warning: When a public repository is made private, public forks of the public repository are detached and put into a new network. They are not made private. For more information, see "What happens to forks when a repository is deleted or changes visibility".