While making sure that Wi-Fi is already connected, go to Settings -> More -> Wireless display on the Redmi Note 4 from which it should start to find any Miracast-supported displays nearby. You should be able to see the Samsung K4300 Joy Smart TV being detected as 'Samsung 4 Series (32)'. Select this TV to start the screen mirroring connection process.
On the TV, select 'Allow' for the TV to connect with the Redmi Note 4.
Once screen mirroring is successful, the Redmi Note 4 will immediately get connected to the TV, where you should see the phone's screen being displayed.
With the Samsung K4300 Joy Smart TV, you can either use Miracast or Google Cast to play YouTube videos from the Redmi Note 4. While Miracast only screen mirrors the phone on to the TV, Google Cast is more selective on the content being projected. As an example, when you select the Google Cast icon on YouTube, only the video will get displayed on the TV and is remotely controlled from the phone.