Other Asian, Australian and South Pacific Frequent Flyer Programs - CI E-Shopping & Dynasty Flyer Miles

Hi all, just wanted to order some Duty Free, but I've read that payments over $55 US, we can also use Dynasty Flyer miles to offload the payment. But I am on the Add To Cart stage, and I do not see any option allowing me to add Dynasty Miles ??, and also do you pre-pay it with a CC, or do the F/A's charge your card inflight??

cheers