Microsoft offers a convenient way to install add-ins for multiple users at once. This is also ideal for companies that globally block access to the Office store but need to make exceptions for certain users and/or apps.
Microsoft has an article here that describes how your Administrator can deploy specific Apps from the store to one or more end-users while still preventing access to the store for all users.
Step 1: In the admin center of your Microsoft Office 365 account, go to Settings > Integrated apps > Deployed apps > Get Apps.
Step 3: This will take open the App Source page. Search for the CloudExtend app. Hit Next.
Step 4: On the next page, select Everyone, Specific users/groups, or Just Me to specify to who the add-in is deployed. Use the Search box to find specific users or groups.
Step 5: Select Deploy.
Step 6: A green tick appears when the add-in is deployed. Follow the on-page instructions to test the add-in.
💡 Note: Users might need to relaunch Office to view the add-in icon on the app ribbon. Outlook add-ins can take up to 24 hours to appear on app ribbons.
Step 7: When finished, select Next. If you’ve deployed to just yourself, you can select Change who has access to add-in to deploy to more users.
👉 Reference: Office documentation link.