1, Go to SET UP >> MARKET PLACE as shown below

2, Click on VETSMS - Text Messaging as shown below 

3, Click on Add configuration details and custom number a number 

4, Now you need to buy a number by clicking search by Location/Number and then click on SEARCH on the right hand side.

5, Select and number by clicking on BUY and then click on SAVE as shown below 

6 , SMS configuration will be activated as shown below 

7, How to enable the SMS for Clients, Go to the Client dashboard and click on EDIT client 

   Add the mobile number as shown below 

   If the client declines to give email address, please check the box as shown below 

Then go to clinic settings - restricted >> Notifiaction >> Click on Appointment >> Statements >> Reminders 
and then click on SEND SMS on ALL 

Step 8>> To enable SMS on a specific phone type 

                 Go to Setup >> Client patient details >> Phone type >> Click on the SMS checkbox against the phone type as shown