The auto-run functionality allows companies with salaried employees to automate their processing and it can ONLY be set up after the first payroll. Auto-run takes away the hassle of processing your payroll and automatically approves your payroll for future paydates. These dates are determined based on the information you put in when running your payroll for the first time.
Auto-run can be activated or deactivated at any time by just setting it to "On" / "Off" when you come to the "Approve" screen of your payroll or through your account settings.
However, it is important to keep in mind that if you want to change salaries, add / remove deductions, additional incomes, etc, it needs to be revised before the payroll processing date i.e. 5 days prior to the desired paydate.