Q: Where do I find the specific files stored on iCloud so I can go in and delete them?

What files, how were they put on iCloud?

You can't.

Manage what is stored on iCloud by following these instructions: http://support.apple.com/kb/ht4847

You can find some of them by going to icloud.com.  All of your iCloud data can be seen and deleted from within the apps on your devices that are signed into your iCloud account.  For example, if your Mac is signed into your account in System Preferences>iCloud and you have checked contacts, calendars & reminders and notes you can open those applications on your Mac and both view and delete the data you don't want.

Go to the System/iCloud preference pane and click on the Manage button.  If you click on each category in the pane you'll see what's in that category.  Items can be deleted by selecting an item and using the Delete button at the bottom: