How to pair iPhone to lg smart tv?

I want to pair my iPhone 6 to my tv to play music from YouTube

Simple answer: you can't.

Apple does not allow Bluetooth to be used that way to ensure the security of the data on your phone and the iCloud network.

Jailbreaking *might* enable you to do so but I have no experience of jailbreaking although the entire point of it is to bypass user restrictions such as that one.