Pricing page would display in your browser. In the Pricing table, under the subscription column of your choice, on the last row, you will see a button, click that button to start setting up your PayPal subscription. You will be redirected to PayPal's website, Login to your PayPal account and follow the instructions to complete the setup.
Once successfully done, you will be charged immediately.
At this point, you would have two subscriptions. The original one you had (before this upgrade) and this one that you setup just now.
