When you order over the phone, you added it to your resort reservation. Your memory maker is then linked to the Primary Guest on your reservation. When you link your resort reservation to your my Disney experience account the memory maker entitlement comes along too. You may run into some issues if person a is the primary guest and person b owns the my Disney experience account. You would have to get it moved to the person who owns the account. Sent from my iPhone using DISBoardsI'm sorry but I don't have a 100% accurate answer for you either, since that is handled by guest relations and vacation planning. From the best of my knowledge go to will call and they will give you the card, then go to guest relations or one of the My Disney Experience kiosks to activate it. Then make sure to keep the card with you so you can get it scanned after you get your pictures and so you can get your attraction photos. Sorry I couldn't help better!
Forgot to add. You ONLY get the Memory Maker card if you order it online through the web site and it isn't strictly necessary. Your order confirmation number can be linked in my Disney experience to link your memory maker card at which point if you do pick it up it's essentially like another PhotoPass card to collect photos on.