WiiM Pro is designed primarily for audio and does not support video casting. This means you cannot cast audio directly from the YouTube app to WiiM Pro. However, there is an alternative method that allows you to cast audio not just from YouTube, but from various apps to WiiM Pro on your Android devices.

Casting YouTube Audio to WiiM Pro from an Android Device

Casting YouTube audio to WiiM Pro that supports Chromecast from an Android device is quite straightforward. Here's a step-by-step guide:

1. Connect to the Same Wi-Fi Network:

   - Make sure your Android device and WiiM Pro are connected to the same Wi-Fi network.

2. Open the Google Home App:

   - Tap on the Google Home app on your Android device to open it. 

3. Play a Video (or Song):

   - Start playing the video or song you want to cast on the YouTube app.

4. Tap the Devices tab on the Google Home app.

5. Select Your WiiM Pro:

   - A list of available devices will appear.

   - Tap on your WiiM Pro to which you want to cast. 

6. Tap the Cast my audio to stream audio to Wiim Pro:

7. Control Playback:

   - You can now control playback (play, pause, skip, adjust volume) directly from your Android device.

8. Stop Casting:

   - To stop casting, tap on the cast icon again and then tap on "Stop Casting."

Note: Ensure that both your YouTube app and WiiM Pro are updated to their latest versions to ensure optimal performance and compatibility.

For a more detailed guide and visual walkthrough, please watch this instructional video. It provides additional insights and tips to enhance your setup experience.