How do I add a custom font to a Shopify marketing campaign, new email template?

Hi - I have created a custom introductory email, see attached picture, and would like to add a custom font to the email (not use the fonts included in the templates). Please can you let me know how to go about this?

I to would like an answer to this. We use Quicksand on our website but this is not available in shopify’s email template design.