An App Catalog within SharePoint will allow you to make internally developed custom apps available for users to install when they browse apps under the From Your Organization filter on the Site Contents page.
- Sign in to Office 365 with your SharePoint Online admin account.
- Go to the SharePoint admin center.
- Select Apps from the Quick Launch bar on the left, and then select App Catalog.
- Select Create a new app catalog site, and then select OK.
- On the Create App Catalog Site Collection page, enter the required information, and then select OK.
- Navigate to the new App Catalog within the SharePoint admin center by selecting Apps and then clicking App Catalog.
- Upload your App by selecting Distribute Apps for SharePoint ->Upload
- Now when you select Add an App->From your organization your App will appear as a choice