The theme features a MailChimp newsletter signup form, located in the subscribe footer bar. To get it work, you need to get your custom MailChimp URL, here is how to do that:

1. Create a new MailChimp account, or log in to your existing one
2. On the start page, select Audience from the left sidebar and click on Signup forms
3. Select the Embedded forms option
4. In the upcoming page, leave everything as it is, and click on Continue button
5. Now your embedding code will present. Scroll it down until you find the <form> tag
6. Your MailChimp URL is the link inside the action="..." attribute, between the parenthenses
7. Enter your custom link to Customizer » Footer » Subscribe in the MailChimp URL field.