To change your Cledara subscription billing details, you will have to go to your Settings > General > Account & Billing.
You can access them by pressing on your profile in the upper right corner, or the settings wheel icon in the bottom left of your screen.
To change the payment method or billing address for your Cledara subscription, click their corresponding Edit buttons and a pop-up window will appear so you can change them.
To finish it off, click on Update. The new details are now saved!