For authentication information, see "Authenticating with GitHub Apps."
Public installation flow
Public installation flows have a landing page to enable other people besides the app owner to install the app in their repositories. This link is provided in the "Public link" field when setting up your GitHub App. For more information, see "Installing GitHub Apps."
Private installation flow
Private installation flows allow only the owner of a GitHub App to install it. Limited information about the GitHub App will still exist on a public page, but the Install button will only be available to organization administrators or the personal account if the GitHub App is owned by an individual account. Private GitHub Apps can only be installed on the user or organization account of the owner.
Changing who can install your GitHub App
To change who can install the GitHub App:
In the upper-right corner of any page, click your profile photo, then click Settings.
In the left sidebar, click Developer settings.
In the left sidebar, click GitHub Apps.
Select the GitHub App whose installation option you want to change.
In the left sidebar, click Advanced.
Depending on the installation option of your GitHub App, click either Make public or Make private.
Depending on the installation option of your GitHub App, click either Yes, make this GitHub App public or Yes, make this GitHub App private.