Deleted iTunes

I accidently deleted iTunes from my iPhone screen. How do I get it back on my screen? When I go to the App Store and enter itunes.apple.com I get an app for "iTunes Store" but when I try to open it, I get a message that says "Restrictions Enabled" and "Certain apps, features, or services can't be seen or used when Restrictions are on. To use this app, turn Restrictions off. I can't locate "Restrictions". I have an iPhone 8 and this is my first iPhone. Can someone tell me how to get the iTune app back on my screen and how do I turn off whatever restrictions are on the phone? I'd like to sync my PC and iPhone eventually. Thanks.