Add-ons must be installed and authorized before you can use them. This guide provides an overview of each of these steps.
Before you can use an add-on, you must install it. Once installed, the add-on becomes available in the G Suite application it extends as a menu item or icon.
You can install published add-ons from the G Suite application, from the Chrome Web Store (editor add-ons only), or from the G Suite Marketplace. Domain adminsistrators can also install add-ons on behalf of their users from the G Suite Marketplace. You can also install unpublished add-ons you're developing so that you can test them.
After installing an add-on, it becomes available in the G Suite application it extends. The first time a user attempts to use the add-on the host application presents them with an authorization card or dialog. This card explains what the add-on needs permission to do for the user, such as accessing the content of the current Google Sheet. The user can then grant those permissions and allow the add-on to proceed. If the user denies the add-on authorization, they can't use add-on.
Editor add-ons use an authorization model that differs from Gmail add-ons. Because editor add-ons operate on Google Drive files, the editor authorization model defines various authorization modes that result when add-ons are used with individual files. When developing editor add-ons, it's important to understand the different modes and how an add-on moves between them.
For more details, see Authorization.
Once you have installed and authorized an add-on, it is available for you to access and use in the application it extends. Editor add-ons usually present at least one menu option in the editor's Add-ons menu that lets users start using the add-on. Gmail add-ons present an icon representing the add-on in the Gmail's desktop or mobile UI; users can start or dismiss the add-on by clicking this icon.
For more details, see Accessing add-ons.