.eww files are IAR workspace files.
For CW10, look at the readme located in the directory at: \kinetis-sc\build\cw\cw_readme.txt for how to get started using the projects with CW10, including setting up the workspace, importing projects, and starting the debugger.
Right now there is only a CW10 project in there for the hello_world example, but you can either copy and paste your own code into that project, or use the make_new_cw_project.exe program to make a new project based off the hello_world one. It would look for source code files in the folder at \kinetis-sc\src\projects\the_name_you_chose_for_the_project
So for example if you choose "lptmr" as the project name, your new project would look for source code files at \kinetis-sc\src\projects\lptmr, which convinently already exists!
The sample code is in the process of being updated for K53 and to add CW10 support by default to most of the projects. Expect to see that soon.