We understand that you've been unable to download YouTube onto your iPhone. We'll be happy to help with this.
It's possible what you're seeing a promoted post or related to the YouTube app. Try tapping on what's coming up to see if there is a link to the app within that. You could also scroll further down to see if the app is below. For more info on downloading apps, check this out: Download apps and games from the App Store
Alternatively, if you've ever downloaded this app before on your account, we could use the previously downloaded section to search for it there. Use these steps: Redownload apps, music, movies, TV shows, and books
Let us know how that goes. Cheers!