To add the "Click to Email" icon on your mobile website, make sure that you have added the email address of your business. This can be done under the Email section of the company information form on the website settings page.
If you have added an email address to website settings correctly, then the "Click to Email" icon (as shown below) will appear on your mobile site automatically.
To learn more about adding an email address in your website settings click here.
To learn more about website settings click here.