Upgrading your account is easy, and can be managed from anywhere in PlayBooks.
After logging into PlayBooks, click on the change plan icon from the top-right of the app, then click on Settings:
Next, you'll see the current plan you are on.
If you don't have a payment method on file, you'll need to add one first. Click Payment Methods and enter your card information.
To change your plan, click on the plan name and then click Edit Subscription. From here you can upgrade your subscription by clicking the drop-down menu, choosing your plan and clicking Update Subscription.
You'll be asked to confirm your payment details after that.
If you get stuck or need more help, just hit the pink live chat icon along the bottom right of your screen.