The error 'IEEEtran.cls' not found indicates that the file IEEEtran.cls is missing from the path. The easiest way to solve this problem is
- Download package IEEEtran
- Extract the package, and you will find IEEEtran.cls inside
- Just copy the file IEEEtran.cls to the same directory as your .tex file
- Run pdfLatex again, and this time the problem is solved