This can be YouTube, Hulu, Netflix, and many other apps. The placement of this icon varies by app, but you’ll usually find it at the top-right corner of the app. Look for the rectangle with Wi-Fi waves at its bottom-left corner. This will open a pop-up window with a list of devices on your network you can connect to. This will connect the app on your phone to your TV. The selected video or song will play on the TV but not the phone, which means you can still use your phone while streaming.

TL;DR in Hindi:
उस एप्प को खोलें जिसे आप स्मार्ट टीवी के साथ कास्ट करना चाहते हैं: एप्प में कास्ट आइकॉन को टैप करें: स्मार्ट टीवी सेलेक्ट करें: प्ले करने के लिए कुछ सेलेक्ट करें: