One of the key new features in Ubuntu 9.10 is Ubuntu One and the ability to sync files into the cloud. This product is developed by Canonical and functions similarly to Dropbox. More information can be found on the website including a FAQ. More here
However, Ubuntu One is not installed as part of a default install of Kubuntu (this is as of the Release Candidate, I don’t know if it might change in release). This post will help explain how to install Ubuntu One and get it working.