You can complete any outstanding payment from the order details in your recent orders list in your account. All the standard online payment methods should be available to by clicking on the ‘Payment’ button in the center of the screen.
If you are heading in-store, you can complete any outstanding payment when in store or by following the instructions above before heading in store.
Please note that it can take 10-15 minutes for the payment & order status to update after you have processed the payment online.