Go to Publish » Downloads » Download HTML for Outlook

Once your file downloads, open it in Google Chrome or Microsoft Edge

Click somewhere on the body of the page and Press Ctrl + A to select everything

Right click and find Copy or press Ctrl + C to copy everything

Go to Outlook

Select New email

Click into the body area of the email and press Ctrl + V to paste

Go to File » Save As

Choose Save as type: Outlook Template

Save your file wherever you like

Use it as you would any other Outlook Template file