Once you have accessed the project you are looking to capture a payment for, navigate to Billing>Capture Payment. 

The Capture Payment box will pop up. Select Auto-Pay and fill in the provided credit card information. Select "Process Payment" once you are complete.

Keep in mind: All manually entered payment methods are available for additional charges for this project. Please ensure you have client approval to charge this card. Manual payments do not use client authorization and, as a result, are subject to dispute. Chargebacks will incur a fee.

The payment will then be automatically charged on the specific date given.