In your welcome e-mail there is a link to download the client, however for some reason that one did not work for me and showed me an error trying to install.
Luckily you can also download the client through your cloud console. Go to your Cloud Services and open the service console.
In the right top, open the menu and select the download app option.
Your download will start and you will see an overview page. Make sure you keep this info, you need the server url later for the sync client.
Run the installer and let the wizard help you install he client.
After the application is loaded, fill in the information from the overview page.
Then sync master will open.
You will see the sync master in the start menu.
You will also see a Documents folder in your favorites.
You can now move files into the Oracle Documents folder.
Use the sync manager to sync the files to the Document Cloud.
You should now see the files appear in the Cloud Console online as well.
So as you can see setting up the synchronization client with the Oracle Documents Cloud only takes a couple of steps.