Final answer:
To make a repository private on GitHub, navigate to your repository's settings, scroll down to 'Danger Zone', select 'Change repository visibility', choose 'Private', and confirm. This feature is free for personal accounts or paid subscriptions.
Step-by-step explanation:
To make a repository private on GitHub, you need to follow these steps:
To make a GitHub repository private, go to your GitHub account and open the main page of the repository. Click on the "Settings" tab at the top of the page. Scroll down to the "Danger Zone" section at the bottom of the settings page. Locate the option "Change repository visibility" and click on it. Choose "Private" and confirm your choice by clicking on "I understand, change repository visibility."
Keep in mind that private repositories are only available for free if you have a GitHub Free account for personal use or if you're part of a team or organization that has a GitHub Pro, GitHub Team, or GitHub Enterprise subscription.