Unfortunately "not working" doesn't really indicate the exact issue. What are you trying? Where does it deviate from expected, and if there are any error messages, please quote them
Starting from basics, read this document to learn how to download apps and games on your iPhone or iPad
Download apps and games on your iPhone or iPad - Apple Support
How to get apps for iPhone or iPad
1. On your iPhone or iPad, open the App Store app.
2. Browse through the Today, Games, Apps, or Arcade tabs to find apps you like. Or tap the Search tab to look for something specific. If you find a game that says Arcade, subscribe to Apple Arcade [at: Join Apple Arcade - Apple Support ] to play the game.
3. Tap or click the price or Get button. If you see the Open button instead of a price or Get button, you already bought or downloaded that app.
In the App Store, if an app has a Get button instead of a price, the app is free. You won't be charged for downloading a free app. Some free apps offer in-app purchases and subscriptions that you can buy. Subscriptions and in-app purchases give you access to more features, content, and more.
Third party subscription sharing depends upon the app. Check for details on the app's description page on the App Store.
For Apple subscriptions, "You can share content that you purchase from Apple including music, movies, tv shows, apps, and books. You can also share your Apple subscriptions including Apple One."
from: What types of content can I share with my family using purchase sharing? - Apple Support - What types of content can I share with my family? - Apple Support