You can either use MSSMS (Microsoft SQL Server Management Studio) or use Database Backups tool from Market Place.
If you use MSSMS then your Server Name would be (LocalDb)\v11.0
Once connected its as easy as selecting Databases > SambaPOS4 right click it and choose Tasks > Backup
Structure of the database for LocalDb might be slightly different I am not sure if it names it SambaPOS4 or not. I should install a localDb version just to check that some day.