I have already set up a class in QBO. How do I assign Payroll to that Class?

If you have already set up class tracking in QBO, you will need to go to Payroll Settings and assign it to track classes for payroll transactions in QuickBooks.
Here is how:

• From the Gear icon on the top, go to the Your Company tab.
• Select Payroll Settings under Account & Settings.
• Select the Accounting pencil icon at the bottom under Payroll Settings.
• Select the Class Tracking pencil icon to enable tracking classes for payroll transactions.
• Under the how do you want to track classes for payroll transactions in Quickbooks tab, you have an option to select:
• “I use the same classes for all employees” box or “I use different classes for different employees” box.
• Done.