You will always have the option to pay an additional amount or settle the full balance, so you can manage your payment whenever it suits you. The process of doing so is:
Log in here
Go to Home
Click on Make a Payment
Choose a payment option
Pay off my balance
Pay any amount
Type out the amount you want to pay
Click Continue to pay
The amount will now be charged on the active card on your account.
Note: At this time, you cannot choose to apply an extra payment to a specific order. However, we can do this manually for you if needed - just contact us.