You can manage your premium subscription from the user profile. It will either display a white box with premium subscription options or a green box with info about your current subscription. If you already have a subscription, you can see its expiry date here.
  1. Open the projects panel and click on your profile picture
  2. Click the Premium button
  3. Pick the subscription type based on your needs
  4. Pick an option to subscribe for a month, a year or indefinitely. You may also activate a 2-week free trial