This tutorial contains instructions how to set up classes in Quickbooks? From this guide, You can easily learn how to set up class tracking in QuickBooks 2015, 2016.
Open your company file.
Go to the Edit menu, then select Preferences.
Select Accounting, then go to the Company Preferences tab.>
Select the Use class tracking for transactions checkbox.
If you want a reminder when you haven't assigned a class, select the Prompt to assign classes checkbox.