Hello,

Please check the articles to find out how to do that with HTML: https://www.campaignmonitor.com/blog/email-marketing/using-phone-numbers-in-html-email/ and https://www.buildableweb.com/article?articleTitle=making-a-clickable-link-to-an-email-address–1294531104–81–howto

As soon as you generate the HTML code, you can add it with the text or HTML widget in Appearance > Widgets.

Best Regards