We're unable to directly integrate QuickBooks Online to Facebook. That means, we're unable also to automatically add the contact details from them.
You'll want to check if you can export the contacts to an Excel file. From there, we can import the file to QuickBooks Online. You can follow these steps:
Go to the Gear icon and select Import Data.
From the list, select either Customers or Suppliers, then click Browse.
Locate the Excel file, click Open, then select Next.