SQL Server is the database program where SambaPOS stores data. If you configure all terminals to connect to the SQL Server they’ll be able to work on a common database.
Windows 8 tablets are same with windows 8 installed PC’s. You need to ensure installed OS on the tablet is not Windows RT version. Microsoft dropped RT versions but still there is a little chance these tablets may exists on market.
What you need to do is installing SambaPOS on two PC’s. Installing SQL Server one of them and make them work together by following these tutorials.