After that install it on your phone.
Open the App.
Click the Backup button in the app and give a name for the backup file and click OK.
Then the app will start to make a backup.
How to Restore Messages in SMS Backup & Restore App ?
Open the SMS Backup & Restore App
Click the Restore Button in the app.
Then select the Backup file which you want to restore.
After that Click OK button. Now your backed up messages will be Restored.