Each computer needs to be logged into the iCloud account and have "Documents & Data" syncing turned on. You can check if "Document & Data" syncing is turned on by checking in the iCloud System Preferences Panel.
You need to create a folder to hold all of your documents and create access to that folder through the Finder Sidebar. You need only create the folder once on one computer, but you will need to add it to the Finder Sidebar on all your computers.
To create a folder:
- While the Finders 'Go' drop down menu is visible, press and hold the option key (alt) which will reveal the hidden "Library" option.
- Select the "Library" option from the list and the contents of the Library folder will be displayed in the Finder.
- Locate and open the "Mobile Documents" folder.
- Create a new folder inside the "Mobile Documents" folder, name it appropriately (e.g. "My iCloud Documents").
- Create an alias of the new folder (⌘+L) and drag it to the "Favorites" section of the Finder Sidebar.
- Repeat steps 1 through 6 (with the exception of step 4) on each computer.
You can now add files and folders to the folder in the sidebar and they will sync between your computers. You can also open the documents within the folder and save any changes you make. You can not currently access this folder from an iPad, iPhone, iPod or iCloud.com