Go to www.popsical.com/premium and press the "Go Premium Now" button.
Login or create a new account.
Click the "Add Payment Method" button and enter your credit/debit card details.
Select a Premium plan that you like.
Make sure the Popsical TV is logged in with a premium account that you just created in order to enjoy the unlimited play time.
The app doesn't need to be logged in with a premium account. Even with a basic account on the app, it can still play premium song as long as it is paired to a Popsical TV that is logged in with a premium account.