Below are the steps to follow to create a new database from a database .bak file:

  1.  Log in to MSFT SQL Server Management Studio
  2.  Right click the "Databases" folder and select "Restore files and file groups"
  3.  In the "To database" field enter the desired name for your new DB
  4.  Select the "From device" radio button then select the .bak file from the directory it is located
  5.  Click the checkbox next to the DB set you wish to restore 
  6.  Click OK and your database will be created from a .bak file