Go to the Saved Modules and click on the Contacts menu item, if it is not already opened on your dashboard. After that click on pen icon, which is located in the header part of the Contacts module as it is shown in the following snapshot
Choose SMS option in the combo box of the available notification types. You will see First Name, Last Name and Mobile Phone fields, which should be filled, especially it is very important to enter a valid number in the Mobile Phone field. Please click on the help icon on the right side of that field to see an example and instructions regarding the necessary format for mobile number. After filling the above mentioned fields click on the Add button. If the phone number was entered correctly you will receive an SMS message with activation code. Also a new row will be added in the contacts table, which will be highlighted with red color, to show that contact is not confirmed yet. To confirm the contact you should click on that row, enter an activation number provided in SMS into the corresponding field and click on the Apply button (see below).
If everything is correct after refreshing the page you will see that the above mentioned row is not highlighted anymore. This means that your SMS notifications are enabled and you’re done with SMS activation. After that you can deactivate/activate SMS notifications anytime by simply checking and uncheking checkbox in the Active column.