To change your payment method:
1) Hover over your Account badge in upper right corner of any page
2) Click on the 'Plans & Pricing' link.
3) Click on the 'Manage your subscription' link.
4) Click on the 'Add payment method' link.
5) Enter your new payment method details and click the Add button.
To change your billing information:
1) From the Manage your subscription page, click on the 'Update information' link.
2) Enter your new billing information and click the Save button.