how can I play sound to the home pod

Use Airplay AirPlay - Apple (AU)

Disappointingly, the Homepod cannot access the Homesharing feature of Mac computers which allows other Apple devices to play music from the iTunes/Music library on a Mac computer and so Homepod Siri won't work.

As advised above, you can send Music from the Mac to the Homepod using Airplay2 but Homepod Siri cannot select this music for you (only simple control such as volume and skip track).

You could consider buying an Apple TV, setting its audio output to the Homepod and accessing the Mac music via the Computers app (Apple TV)and Homesharing (Mac). Homepod Siri seems to work most of the time for me with this configuration.

I have my original Homepod set up, Siri will give me the time and answer other questions but does not have any music in an album. How do I get Siri to play music from the homepod?

Siri on HomePod can play from your unhidden purchase history, or your iCloud Music Library if you have a subscription to Apple Music or iTunes Match.

tt2