Open the file "shelf_metals_presets.mel" in a text editor (like notepad) and find the words "your_script_path". Replace them with the path to your script (typically: C:\Documents and Settings\USERNAME\My documents\maya\version#\scripts where USERNAME and version# have to be replaced with the proper values).
A couple of comments to you though: If you really are so new to computers that basic things like files and strings and paths etc are confusing to you, you are really going to have a lot of frustration learning Maya. You might want to consider something a little more accessible - Sketchup is getting really good reviews - for a while and once you get more comforable then move over to Maya etc. I don't say this to be rude - its just that I've seen a lot of people jump right in and when they don't get any kind of result they give up. If they'd just start with the basics, everything would probably go better for them and they'd stay with it. (I've been doing this for about 12 years now and I've still got tons of things I'm unclear on)
Also - you've posted to the Aliasstudio forum - not a Maya forum. Don't feel too badly though, the only people who post here are those who think it is a Maya forum and a couple of us who lurk hoping that someday something actually related to studio might pop up.
Cheers,
MUTTOAB