All you need to do is print the voucher (there's a link on the page) and then present it at the checkout when you're paying for your purchases.
I thought I'd share it as £5 saved at the airport is almost 2 Efes, I know where I'd rather spend that £5 lol!
Anyway, here's the link;
http://wdfonline.com/WDFVouchers2011/5Q ... MI,2NEEN,1
