Northwind sample database that can be downloaded as an executable sql script or as a backup that can be restored with sample data currently works with SQL Server 2005/2008/2012/2014/2016/2017
You need to login to your SQL Server, then right click on the database -> select Restore Database
Next select your backup database file
Next, You need to enter your database name that you want to restore
Click OK button to finish
If your backup file is a script, you need to open the script file with SQL Server Management Studio, then press F5 to restore the database from the script.