Cast to TV

Hi All,

I have a Nexus 6P running on Android O. I want to stream a movie on my screen to my LG Smart TV. I have tried to use the "Cast" function on my phone whilst my Phone and TV are both connected to the WiFi, however every time I scan a device to cast on, it says no devices were found. I'm fairly new to this sort of stuff and I don't know if I need some other sort of applications or anything like that. Any help will be much appreciated!
Thanks, Liam 👍