The load test fails because the uploaded file has not been zipped together with the load test program.
You have to copy the uploaded file into the same “Project Navigator” directory as your load test program.
After that, you have to ZIP the compiled class (*.class file) of the load test program together with the uploaded file (and optionally together with your Input Files and Plug-Ins) to one ZIP archive by using the ZIP functionality inside the “Project Navigator”.
After that you can start the load test by clicking on the Execute-Icon of the newly created ZIP archive.