Eclipse is an integrated development environment (IDE), primarily for programming in Java, but which can be used to develop in C++ with the appropriate plug-in modules.
Install Eclipse Galileo. Run Eclipse and apply any Eclipse updates via Help -> CheckForUpdates. Then, install the C++ tools via Help -> InstallNewSoftware. To find the CDT (C and C++ Development Tools), choose WorkWith: "Eclipse Galileo Repository". Under the Programming Languages menu, enable "Eclipse C/C++ Development Tools". Press Next and wait while Eclipse downloads the modules it needs. Press Next, Accept, and Finish. Then wait again while Eclipse completes the installation. Finally, restart Eclipse.
You are now ready to use Eclipse to develop KDE in C++.
Carefully read the detailed, but brief, installation instructions (at http://qt.nokia.com/developer/eclipse-integration) for your development system.
But very basically it involves downloading the Qt tarball, unpacking it under /usr/lib (or other similar location where Eclipse components are installed), and starting Eclipse (with the -clean option for the first time).