I can find the app on my phone after downloading

Use App Library to search the Wallet app, see -> Organize the Home Screen and App Library on your iPhone

Organize the Home Screen and App Library on your iPhone - Apple Support           

• If you have find the app, tap & hold on the app, then drag to the Home screen & drop it.

see -> Organize the Home Screen and App Library on your iPhone

Organize the Home Screen and App Library on your iPhone - Apple Support           

From your Home Screen swipe left to the last screen.