I'm trying KDevelop 4.6 in Fedora 20 and am very impressed so far. The single problem I have is how to add existing files to an existing project. I Googled but can't find an answer. I have project filters set to include all .cpp .h files. I copy my files in the file system to my project area, but cannot see these files in the relevant project folder in Kdevelop. In the project menu, I do not see an option to add or import existing files.

How do I add existing files to a project?

You should be able to simply copy them to the project directory, or use one of the methods to create new files. If that doesn't work, it's a bug -- sometimes the cmake project manager gets stuck and doesn't update the file list ...
You can try clicking reload in the context menu, or restarting KDevelop (not ideal, I know). If it's reproducable, please report a bug on bugs.kde.org.

Greetings!

Thanks for the quick reply. Is the KDevelop notion of a "project" independent of my project's CMake build files? Or does KDevelop use CMake to construct an independent view of the project? I'm sure not why CMake is a part of the story.

For KDevelop, a project is simply a directory plus a build system (CMake) plus a VCS, or so. Usually all files in that directory are part of the project unless they are excluded by the project filter.

CMake is part of the story mainly to find the include paths for your project automatically, and to provide some integration with cmake (add new files to targets automatically etc).