You can do this either of 2 ways:
(1) Register via their website here or (2) simply print the original coupon, take it in-store and grab 2 FREE bottles of shampoo & conditioner. Either way, you get the same coupon with the same bar code.
Also posted on their Facebook page here.
Confirmed working by me and 2 colleagues in Melbourne CBD.
Enjoy :)
Does that mean you need an original voucher