The Premium plan is offered through the in-app purchase. Navigate to:

(1) Setting 

(2) Premium Plan and 

(3) select a subscription period from 1 month or 12 months.

Remember, the Premium plan is a non-renewing subscription. At the end of subscription period, you'll need to renew one manually. Thus, you credit card will NOT be automatically charged when your subscription expires. We will send you a friendly reminder when your subscription gets close to expiration.