as far as I know the library is not released to even alpha yet, so you need to download the entire toolchain for AndroidX development + downloading the Preview Android Studio, this is the guide:
https://android.googlesource.com/platform/frameworks/support/+/refs/heads/androidx-master-dev/ui/README.md
it doesn’t seem to have any guide at the moment, but there are many examples that you can find inside the demo source code, covering many different usages of Compose.
I suggest to just follow the guide above and get it to compile then learn through the examples in it (
that’s what I did, it’s very helpful)