Go to your template by going to Settings > Emails and Texts.
Click on the template that you want to edit that's under the Email Templates section.
Within the Body section, type a phrase or word to attach your link to.
Afterwards, highlight the phrase or word you typed in and click on the chain icon or you may simply do Ctrl+K.
A new pop-up window will appear. Under the field "To what URL this link should go?", enter/paste your url.
Click on the Insert Link button.
Don't forget to click the Save Changes button to apply your changes.
How to add links to your automated emails