Need to add a payroll service. How do I add to existing account??

I'll guide you through adding a payroll service to your existing QuickBooks Online (QBO) account, @jcarter5779. 

Let's go to the Employees tab to achieve your goal. I'd first suggest having your essential payroll and tax information handy. You can get them from your previous payroll provider, own records, accountant, or federal and state agencies. For more details, see this article's What you need before setting up Payroll section: Payroll Setup Overview.

Once prepared, proceed with the steps below. 

1. Go to Workers from the left menu.
2. Select Employees.
3. Click Get Started.
4. Choose your payroll plan. 
5. Follow the on-screen instructions to complete the setup process. 

The screenshot below shows you the first three steps. 

After that, you'll be able to see the Run payroll button on the Employees page. View the screenshot below for your visual reference. 

I recommend visiting this website: Getting Started With Payroll. It contains articles that'll help you manage employees, process payroll, pay taxes, and file tax forms using the program. 

I'm here anytime you have other concerns. Wishing you and your business continued success, @jcarter5779.