Click on the Settings link next to the QuickBooks toggle to access the QuickBooks settings.
Default QuickBooks Service - Choose which default product/service you would like your services to link to by default, this can be later customised within each service item you create. This is what determines which GL code each service will be linked to.
Client Name Sync - If client name sync is on, then when new invoices are created in QuickBooks Online by Practice Ignition, the name in QuickBooks will be updated to match Practice Ignition.
Recurring Invoice Terms - This will set the due date on your recurring invoices to that number of days after your default company invoice day.
Note: If you haven't already enabled payments - turn on Payments.