File | Open
This option brings up a standard Windows Open dialogue box. You can select the markbook file you wish to load into the grid. For meaningful results, it must be a file which has previously been saved by this program.
The outcome of trying to open any other type of file is undefined. The software does not check the file type, and an .mbk extension is not needed.
Once opened, you can edit the grid, add a new set of marks, or produce printouts. If you subsequently Save the file, your alterations will be saved, overwriting the original file. You can Save As to a new file if you wish to keep the original.