how do I clean out my iCloud?

You get a broom.

So what is it exactly you want to "clean"? What are you trying to do?

If your iCloud storage runs low, there are several ways you can increase your available space.

Here are some general suggestions, as well as some specific ones:

iCloud: iCloud storage management overview

iCloud: Reduce email storage space

iCloud: Delete photos and videos to save storage

iCloud: Back up fewer apps to save storage