How to Install the Add-In App Across Multiple Site Collections
About
The App Side Loader application facilitates the deploy of valid Add-Ins App through a site collection in SharePoint Online or SharePoint On-Premise.

The tool can be found in the download package:
Requirements
- The Add-In App must exist in the App Catalog
- Must be run by a Tenant Admin / Site Collection Admin
How to Install the Add-in App
- Download a copy of the Add-In App from the App Catalog, if not already available.
- Launch the Side Loader Application.
- Select the SharePoint version.
- Enter a Tenant Admin user for SharePoint Online or a Site Collection Admin user for SharePoint On-Premise.
- Enter the password.
- Enter a site collection URL.
-
If AutoFetch Site Collections option is enabled, provide the SharePoint Online tenant admin URL.
Note: The AutoFetch Site Collections option is available only for the SharePoint Online version.
- Enter the location of the Add-In App.
- Click Connect.
- After the sites are loaded, select the sites that you want to modify.
- Right-click in the tree section.
- The menu from the image below appears.
- Select the action you want to perform.

If the AutoClassifier App appears as successfully added on your site it does not mean that the full installation is completed.