How to restore non App Store items to iPhone in the new iTunes and iOS 11

If you have media on your computer that you can’t redownload from the App Store or iTunes Store directly on your iOS device, such as custom ringtones or iOS apps, you can drag and drop the media from your computer to your iOS device using iTunes.

1. Connect your device to your computer.
2. Open iTunes. Make sure that you have the latest version.
3. On your computer, find the item you want to add to your device. If you’re looking for Apps, Tones, or Books (for Windows) that previously appeared in your iTunes library, you can find them in your iTunes media folder.
4. Drag the item from your computer to your iOS device in the left sidebar of iTunes.