I tried to set up HP Photosmart C4580 printer/scanner/copier with my Airport Extreme. However it is not connecting to the Airport Extreme. Diagnostic check recommends temporariiy disabling the Mac Address filtering on my Airport. However, I can't figure out how to do that! thanks

MAC address filtering is used to prevent unauthorised people getting access to your wireless network. you need to get into the Airport Extreme configuration using Internet Explorer or any other browser, then select wireless setup then MAC address filtering. You need to turn off MAC address filtering.
Check your manual on how to configure your Airport Extreme.