Next make sure your header file and its corresponding .cpp file are in the same directory, unless you've got your compiler configured to search certainly and not by default. Actually, what compiler you using? Is it command line or IDE GUI? Let me know.
Ok sorry I figured it out. I had to put #include <fstream> and using namespace std; in my header file and now it works fine. And I did what you said about putting all the files in a project. So sorry again and thank you for all your help.