It’s much the same for Music, though for some reason you add them via the Music sticker. You can pick whatever is popular at the moment, or search for the exact one you want in the search bar. Once you found the one you want, you can use specific parts of it, and even add lyrics to them when you use it as part of your Instagram Stories. Naturally, you can also choose the way they show up on your Stories.
Both Reels and Music are now already available on the Instagram app for Malaysian users. If you don’t see it, either the app needs an update. Either that, or it’s still in the process of being rolled out in the background.