There are currently two subscription types: Premium and Premium Plus.

Premium subscription provides you with the full access to the extensive catalogue of items and customisation possibilities. 

With the Premium Plus subscription, you can access your account and projects on other platforms (Web, Android, iOS, macOS) and create HD renders.

Subscription in the Windows app is a one-time purchase, so you're getting lifetime access to the catalogue by upgrading a subscription plan.

Depending on the platform and market region prices may slightly differ.

Open the app on your Windows device. In the left menu at the bottom, you can find the "Upgrades" section. Open that section to choose and purchase a subscription plan. That is a one-time purchase that gives you lifetime access.