I recently deleted an app. How do I retrieve it?

Open the App Store app on your iPhone, tap Apps at the bottom of the screen, tap the round user icon at the top right of the screen, tap "Purchased" and then tap "Not on this iPhone." Scroll to the app and tap the cloud with down arrow download icon.

Redownload apps, music, movies, TV shows, and books from the iTunes Store, iBooks Store, and App Store - https://support.apple.com/HT201272