How to do SMS Integration in erpnert?

How to integrate the SMS in erpnext; when the sales invoice is submitted.
I submit the sales invoice and click the button (sent SMS) and it will not send the SMS…

Welcome to forum Barath.
To configure a SMS you should first configure your SMS settings,

Follow the Document : SMS Settings

Then you may configure notifications to send SMS as follows,

Follow the document : Notification

This works if your ERPNext version is 13 or 14, prior to that to send a SMS you may need to write scripts.

Hope this helps.