Before you can proceed with using this feature, there’s a few things you should know and do:
– this feature is only available on devices running Android 5.0 or later
– this feature is not supported on iOS or Windows devices
– it’s better if you turn off “Power Saving Mode” on your Android device. Why? Because it can limit the processing power of your device, which consequently might affect the performance of the Cast Screen feature
Turn on “Microphone” permission
Lastly, turning on microphone permissions from the Google Play Services app is necessary in order to successfully use the “Cast Screen / Audio” feature with Chromecast. In fact, if you don’t have said permission turned on, the Cast Screen session will disconnect right away after trying to connect.
Now, do the following to turn on microphone permissions:
– on your Android phone or tablet, go to Settings
– now scroll down and tap Apps > Google Play Services > Permissions
– then, look for “Microphone”, and slide the slider On
Cast your screen from your Android device to your TV
Now, let’s get to the topic you came here for. Follow the steps below:
– first, make sure your smartphone or tablet is connected to the same Wi-Fi network as your Chromecast device
– open the Google Home app
– now tap the device you want to cast your screen to
– then select Cast my screen icon > Cast screen
Adjust the volume
If the volume is too loud/low:
– open the Google Home app again
– tap your device, then adjust the volume
Stop casting your phone/tablet screen
Stopping the screen mirroring is as easy as it is starting it. Here’s what you should do:
– open the Google Home app
– select your device > Stop mirroring
Source: Chromecast Help