How do I set up parental controls on my daughter's iphone?

I have a 14 year old daughter who has developed a seriously annoying addiction to social media and other apps on her iPhone. Recently she got in trouble and I am taking control and limiting her access to SnapChat, Instagram, and other apps on her iphone, plus the ability to download stuff. How do I set up parental controls and can I do it from a central place or does it have to be on her phone? Also, how do I prevent her from changing the unlock passcode to her iphone? She changed it and I had to yell at her to tell it to me. Is there a way to prevent her from changing it again? Any help would be great. Thanks. Signed, frustrated parent of a social media and snapchat "streak" addict