You can go Premium or buy SuperCrush directly from the in-app store, in the top right corner of the “My Account” page by tapping the “+” button or on the "Need SuperCrush" button.
Whenever you tap a button leading to a paying feature (e.g. List of people who have Liked you), the app will suggest you to go Premium.
You will then see a carousel in the top part of the screen which will list all the Premium advantages.
Different types of subscriptions are available, with various lengths. Purchases can be made via your iTunes or Google Play account. For this you will need your username and password.
If you get a multi-month subscription, the total amount corresponding to the entire subscription period will be charged all at once.
Moreover, please note that subscriptions are renewed at each period term unless you disable the automatic renewal on the App Store or Google Play Store.