What audio equipment are you using and what computer do you have? I think the simplest was to explore streaming is to connect an existing computer to your audio system. The very low cost way of doing this is with a headphone (3.5mm) to RCA cable. The 3.5mm plug goes into the headphone jack on the computer and the RCA plugs go into one of the non-phono inputs of your audio system.
Then you decide where you want to source your music from. Apple, Tidal, Spotify, Quobuz, Amazon are some of the sources for music. You create an account (some have free and/or trial options), pick your music, press play and music comes out your audio system.