Power Apps now supports creating an app from data stored in lists on a SharePoint 2013 and SharePoint 2016 on-premises site.
Below are the steps for creating a Power App based on on-premises data
1. From the Power Apps studio click New from the left navigation bar.
2. Under “Create app from your data” select SharePoint.
3. In the next screen select “Connect using on-premises data gateway” to connect to SharePoint on-premises.
4. This would display additional fields for connection details.
5. From the Authentication Type drop down choose your authentication type. Currently Windows and Basic authentication are supported for SharePoint on-premises.
6. Provide user name and password for the connection.
7. A gateway is required for creating an on-premises connection. If you don’t already have a gateway, you can create one by following the details listed here.
8. Click “Connect” button to create the connection.
9. In the connect to SharePoint site page enter the URL of SharePoint on-premises site and click Go
10. This would display lists within the site. Select the list based on which you want to create the Power App and click Connect.
11. The App screens with the fields form the list you had selected will be created.
12. You can make required changes to the field and layout and save the App.
When you share a Power App that uses SharePoint on-premises connection, the gateway used by the SharePoint connection will also be shared implicitly.