If you have a paid account, you can convert your public repositories to private ones.
Tip: If you are on the free plan, or have no private repositories available, you will need to upgrade before you can switch the repository to 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".
On GitHub, navigate to the main page of the repository.
Under your repository name, click Settings.

Click Make private.

- Read the warnings.
- Type the name of the repository that you want to make private.
- Click I understand, make this repository private.