The Send By SMS feature is available for all of the Save & Share buttons. To activate it, go to Installation, scroll down to the "Save & Share" section, click Add, select whichever button you would like to enable the SMS feature for, find the "Select your button's features" section, then check the “Send By SMS” option.
*You need to have communication credits on your account for this option to work. For every SMS that is sent, a $0.10 fee will be deducted from you communication credits.
To see how many communication credits you have left, click on your account in the upper right hand corner then "Payment and Budget". Toward the top right corner under the “Your communication Credits” section, your current balance of Communication Credits will be shown.