How to store Mac documents in the iCloud?
You cannot treat iCloud as some sort of internet filesystem like Dropbox.  The only way to place data into the iCloud system is via an iCloud enabled app.  There is no generic way to access your iCloud files except via the application that put the files there in the first place.

So, in order to use iCloud, use iCloud enabled apps.  Use the same apps on 2 or more Macs, and that is how you share docs/data.

I'm not sure when the Mac iWork apps will get iCloud, I suspect in the next version which is now sorely overdue.