To enable SMS Text Marketing click on Settings>Campaigns>Keyword.  This allows you to start sending SMS text campaigns to your clients who have a mobile number and have opted-in to receive marketing communications with you.  

Choose your keyword.  You may need to try multiple times if you are choosing a keyword that is popular like "PIZZA"  The keyword you select is going to be one of the ways your customers can opt-in to your text campaigns.  Note:  text "PIZZA" to 85100 to sign up for my text promotions.  Customers must always double opt-in by replying Y or Yes to the initial welcome text they receive from you.

You can also include an initial opt-in offer to all new customers who have opted-in to your marketing messages.

Campaign Settings Video