The payment methods option on your invoice is part of the QuickBooks Payments feature, which needs to be activated first before it becomes visible when generating an invoice.
Here's how to activate it:
Open or create your invoice.
Scroll just below your line items to the Customer payment options box.
Click the blue Activate payments link.
Follow the on-screen prompts to link your account or sign up for QuickBooks Payments.
Once activated, these payment methods will turn from grey to full color on your invoice.