homepod

HomePod Stereo

I have two HomePods but I know that when I want to listen to music from the internet from Imac on Safari I can't activate the stereo functionality.

When I go to the volume icon I get the two HomePods to be selected but I can't make them play together

From Specify if you go to the Youtube well site in Airplay I am only looking for external TV sources but I am not able to activate the stereo function HomePod

some succeeds in iphone instead