To send SMS from the application, you must configure the SMS driver in app's configuration panel.

Go to Configuration Page and click on the SMS to go to SMS Configuration

Connect Configuration - SMS - Log, Twilio

The log driver doesn't send any SMS. It only logs the SMS in storage/logs/laravel.log file

To use the Twilio driver, you must have valid & active Twilio account. Once ready, you can use your SID, Auth Token and Twilio number to send SMS.