To cast your phone screen on your TV you need to have Chromecast.
Follow the steps to successfully cast your screen-
Before you begin casting
Cast from Chromecast-enabled apps to your TV
Note: The Cast button isn't located in the same place on all Chromecast-enabled apps.
You can now cast videos, movies and TV shows directly to your TV.
To stop casting, tap the Cast button and then Disconnect.
You can also watch this step-by-step guide to do the same
You can check more details here : Oppo F11