Why not use Setup Assistant to migrate your apps and data & settings? You passed it up when you turned on the MBA for the first time, how you can get a second chance but it will mean starting all over. Please look over Pondini's instructions in Lion Setup Assistant tips.
If Aperture is all you're interested in you will need the security key and need to re-download from the App Store. You should be able to find Aperture in the purchased tab, then simply re-download it assuming you're using the same Apple ID as the original download.