Hello Paul K! I'm Jeremy and I'd be happy to help you with your question.
"To turn on an add-in, do the following:
Click the drop-down menu on any email message in Outlook.com, and then select Get Add-ins.
On the Add-ins for Outlook page, select the add-in. For free add-ins, click Add. For paid add-ins and free trials, select Get it to finish your purchase."
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Regards,