Please help am a new user and very stuck

so i bought the chromecast audio to help control a wiring system i have. i want to use the CCA to stream all local speaker content on my computer. its the only reason i bought it.

the chromecast web abb gives me an unable to capture media contents when i try to go cast screen

so far it looks like Chromecast Audio Stream is the best bet. i try it and nothing happens.

plex gets stuck on loading when i switch to streaming.

any help is appreciated. i just want wireless speakers for my computer. that is all. i only use vlc to play files