Download the file QTLCartWin.zip in binary format to your computer's hard drive. Move the program to a directory where you want QTL Cartographer to reside. Use an unzip utility to unpack the MS-Windows distribution (often, this can be done with a double-click).
The programs will be unpacked in the directory you choose. You will want to do this in a directory created for QTL Cartographer, so let's assume that it is c:qtlcart.
You may also want to download Gnuplot for MS-Windows. In binary format, get the self-extracting archive gnuplot.exe. Put it in a subdirectory (say C:gnuplot) and while in that subdirectory, run gnuplot from the DOS command line.
The programs can be run by double clicking their icons in the Windows Explorer application. An alternate method is to open a Command Window and type in the program names.
You can view the output files in any text editor, although you should be aware that some editors in MS-Windows cannot load large files. The Notepad application provided with the current (21st century) versions of Windows should work fine.