You can access the My Subscription window from the switcher. 

If you have a single subscription, you will directly see the Subscription Summary. If you have more than one, you will have to choose the Subscription you wish to manage as shown below. 

In this screen, you can directly access Payment Information, Billing Address, Shipping Address, and more here.

You can edit your Payment Information from the widget below.

Credit card
You can find your current credit card details and the option to edit it in the Payment Information module. 
Enter your new credit card information and 
Update Payment Method

Once you confirm,  the credit card will be saved.

Similarly you can manage your Billing Address,Tax ID,Billing Name, Billing Email, and Billing Company  too.

You can also manage Shipping Address.