Hi the mel script should be put in your scripts directory , the path should be something like C:\Documents and Settings\your name\My Documents\maya\scripts

To get the script to work you will need to source the script or restart Maya.
You can execute external script files in two ways:

1 In the Script editor, select File > Source Script.
If you change a script after sourcing it, the change is not automatically picked up by Maya. You need to re-run the script with File > Source Script.

2 If the script is in one of Maya’s standard script directories. When you type the name of the file in the command line and hit enter, Maya will source the contents of the file, and if a procedure with the same name exists in the file Maya will execute it.

You will most likely need to create a shortcut to use the Mel script so type the name of the script in the command line then middle mouse drag it to the shelf and then in future to use the script just click on the shortcut.