1) Notepad is an application, not a file.
2) If you meant to mean you are opening a text file created from Notepad, then
a) Review the file_open commands and the associated constants that are defined within WinRunner (FO_MODE_OPEN does not exist as a constant)
b) once you open a file, you aren't going to want to open it again.
Any and all of the information you need to review is at your fingertips with a press of the F1 button.
Have you also gone through all tutorials and information shipped with WinRunner to your company? Have you identified a mentor within your company to help you though your training of the tool?