From the inbox homepage, click the Browse Add-ins icon on the toolbar at the top.
Within the pop-up window, click the search bar
Search for “Everest” and click “Add”
In the “Custom Addins” section, click on ‘+ Add a custom add-in’ button and select ‘Add from URL…’ and copy, paste, and submit the following link:
https://everest-automail.vercel.app/outlook-manifest-production.xml
After adding, the add-in will either be already visible in the toolbar or it can be found by clicking '…' icon in the toolbar like before. NOTE: If the button is greyed out, please select an email first before using the add-in