Office 365
If you want to deploy the Office add-in centrally to all or a certain subset for your users, there are two options. If required by the guide, please use this AppSource listing: Office Add-in in AppSource
Via Office 365 admin center
Please check this guide in the official Microsoft documentation on how to do this.
Via centralized deployment Powershell commands
If you prefer to use powershell commands, you can use this guide.