If you have .pl files associated with the Perl interpreter (you get this by default with Active Perl), all you need to do is double-click on the mapshipment.pl file. It will then prompt you for a tracking number. If you don't have the .pl file association, you can run it from the command line.
To run from the command line, open a command prompt (Start | Run | cmd on Windows NT/2000/XP, and Start | Run | command.com on Windows 95/98/ME). Change to the directory where you saved mapshipment.pl. At the command prompt, type:
perl mapshipment.pl <your USPS tracking number>
c:\Perl\bin\perl mapshipment.pl <your USPS tracking number>
mapshipment.pl <your USPS tracking number>
If you don't specify a tracking number on the command line, it will prompt you for one.