iCloud Find my mac issues: this mac cannot be located because it does not have wi-fi

I am using a mac book pro from 2008 and I just recently udated to mountain lion. I tried to set up find my mac and I'm getting an error message that says "This mac cannot be located because it does not have wi-fi". I use wi-fi to connect to the internet so I'm not sure what that means. Could someone explain this to me???