OK - that’s good, although not sure how you ended up here if you had a HT setup beforehand! You have to build this starting from the Playbar, so:
- In the settings for your current stereo pair, choose to remove Sub and accept the option to move it to the Playbar.
- Separate the stereo pair. (If either is called ‘Family Room’, rename it to something else}
- In the Settings for the Playbar, add surrounds, and follow the prompts
- Change the name from ‘Garage’ to ‘Family Room’
Edit: might be better to swap steps 3 and 4 but I don't think it will make any difference