Follow the steps to cast YouTube Kids App through Chromecast:

1- Setup: Ensure your Chromecast-enabled device and your iOS device are connected to the same Wi-Fi network.

2- Install YouTube Kids App: Download and install the YouTube Kids app from the App Store.

3- Open YouTube Kids App: Open the YouTube Kids app and set up the app if you’re using it for the first time.

4- Choose Video: Select the kids’ video you want to watch from the YouTube Kids Library.

5- Casting: Look for the casting icon within the YouTube Kids app. This icon is usually located in the top-right corner of the playback screen. It’s often represented by the Chromecast symbol.

6- Choose Chromecast: Tap on the casting icon, and a list of available devices to cast to will appear. Select your Chromecast-enabled device from the list.

7- Start Casting: After selecting your Chromecast device, the kids’ video should play on your TV.

Or 

1- Open Browser: Launch your Cast for Chromecast browser on your iOS device.

2- Go to YouTube Kids: Visit the YouTube Kids website (www.youtubekids.com) using the browser.

3- Video Selection: Select the video you want to cast from the YouTube Kids website.

4- Choose Chromecast Device: Choose your Chromecast device from the list of available devices.

6- Start Casting: The app will auto-detect the castable links. Tap on the link you want to cast. The video should start playing on your Chromecast-connected TV.

7- Playback Control: You can control the playback, pause, and play the video using the controls in the browser.