Use of scripts is detailed in the Adobe Illustrator Help files:
http://helpx.adobe.com/illustrator/using/automation-scripts.html
A simple Google search for "How to use a script in Adobe Illustrator" or a search of the help files for "scripts" would have both turned up results.

To use that script (or any script for an Adobe application)....

• Copy that script code to a text file
• Save the text files as plain text (you can not use Word for this) and title it whatever you want adding a .jsx suffix. So the final file should be something like "AddStrokes.jsx"
• Place your .jsx file into Adobe Illustrator CSx/Presets/[language]/Scripts
• Relaunch Adobe Illustrator

Now open your artwork, select some objects and choose File > Scripts > AddStrokes (or whatever you titled your file).

For the record that script does function correctly. At least in Illustrator CS6.

Use of scripts is detailed in the Adobe Illustrator Help files:
http://helpx.adobe.com/illustrator/using/automation-scripts.html
A simple Google search for "How to use a script in Adobe Illustrator" or a search of the help files for "scripts" would have both turned up results.

To use that script (or any script for an Adobe application)....

• Copy that script code to a text file
• Save the text files as plain text (you can not use Word for this. You need a plain text editor - on Windows use Notepad, on a Mac use TextEdit) and title it whatever you want adding a .jsx suffix. So the final file should be something like "AddStrokes.jsx"
• Place your .jsx file into Adobe Illustrator CSx/Presets/[language]/Scripts
• Relaunch Adobe Illustrator

Now open your artwork, select some objects and choose File > Scripts > AddStrokes (or whatever you titled your file).

For the record that script does function correctly. At least in Illustrator CS6.