Is my music stored in the Icloud? If so, how do I access it?

It depends on what you need.

If you only want the files to be backup somehow, you can place them in Documents folder on your Mac, for exemple, or a folder synchronized in a Windows PC.

Those files can't be played with Music app on your phone. To do that you'll have to put them on Music/iTunes library and sync them with your iPhone.

You can also use Apple Music service and sync your local Music library with it. Once done you'll have access both to your music library and also Apple Music service library combined. Have in mind Apple Music is a monthly subscription service.