All sites include an editable footer navigation. 

You can add links to them just like other navigation lists  but they come already set-up with 2 links; terms and service and customer service. 

The Terms and Service will take them to a page with the terms you set up in your settings. 

The Customer service link will open up the email service on their computer with an email filtered with your email in the to field. To edit that email address check your account settings.