Thank you for posting your query on the Community.
To advise on how to to do this, can I first confirm the version of payroll you are currently using in QuickBooks Online - Standard, Advanced, or Paysuite. If you are unsure how to check let me know and I can guide you.
Simple Start currently has three payroll software in use - Standard, Advanced, or PaySuite.
If you are using the standard payroll, when you select the 'Employees' tab on the left hand menu you will then have two seperate tabs - one labelled 'Payroll' and one 'Employees'.
If you are using PaySuite this will show 'Powered by PaySuite' on the top-left corner of the employees homepage.
The Advanced payroll will show with the option to 'Run payrun' on the employees homepage.