Setup
1. Download Google Home APP.
2. Set up a new home.
3. Set up a new device
4. Select a home.
5. Select your speaker.
6. When found the speaker will beep.
7. Name speaker.
8. Confirm setup is correct.
9. Finish.
Casting
Once the setup is complete it will then show your speaker within the Home selected i.e. Office.
Select the speaker and start casting. You can then add multiple speakers within that home and all speakers will play at the same time.
Attached is a video showing exactly how-to setup your Google Home.