SMS messages are a way to quickly deliver offers or upcoming news to members of the Loyalty program. Once SMS has been configured when the Guest is signing up thru the App they will be prompted to enter their phone number.
The Guest can also enter their phone number if the eClub signup.
When their phone number is entered upon signup the Guest will receive an SMS from the configured Shortcode. See the below article for a Guest to input their phone number if their already a member of the Loyalty Program: