Hit the “Add integration“ button on the admin page to get to the form below. To setup a GitHub integration with Private Packagist start by selecting "GitHub" as the platform and enter the URL of your GitHub Enterprise Server or https://github.com to use the public GitHub server as seen in the example below. A link to setup the OAuth application on GitHub will automatically be displayed.
Do not submit the integration form yet, but copy the content from the "Callback URL / Redirect URL" and follow the setup link to your GitHub server. The fields Client ID and Client Secret remain empty for now.
Register a new application on GitHub. This will reveal the client ID and client secret required for finishing the setup on Private Packagist.
Copy and paste the "Client ID" and "Client Secret" values back into the Private Packagist integration form and submit the form with the "Create Integration" button.