Swipe down on the Home Screen to open Search
Type the app name
Press and hold the app icon
Tap Add to Home Screen if shown
Open the App Library by swiping left to the last page
Find the app in the App Library
Press and hold the app icon
Drag it to the Home Screen
If the app is hidden, check Screen Time restrictions
If the app is deleted, reinstall it from the App Store
If the Home Screen is full, move an app to another page or folder first