How to pay pending invoices using credit card?

a) Open Google Chrome or Firefox
b) Login to https://selling.channelmax.net/
c) Click on "Settings-->Account-->Billing" 
 1. Click on "My Invoices" tab
 2. Select the unpaid invoice
 3. Next, click on the button "Pay With C.Card" and proceed, it's self-guided. If you have not saved your Credit Card details add them as per this link.