To view a subscription, click the "View" button circled above in red. You will be taken to a page with information about your subscription and actions you can take with your subscription. At the top of the page you will see subscription information followed by actions you can take with your subscription:
Clicking the "Change Payment" button will take you to a page with information about your current subscription and the different payment methods you can use for your subscription:
From here you will fill out your payment method as if checking out. Select an option and then click "Change Payment Method" to proceed. You will be taken to PayPal if chosen or receive a pop up to enter your credit card information if the stripe option is chosen.
Once this step is completed the payment information attached to your subscription will be updated.