The way the trade up works is after you order, you will be emailed a RMA that will explain how & where to ship the old items you are trading in. If you need them until the new products come, tell us in the comment field when you place the order.
Also, it seems I now have to say the following: This Trade Up program is a heck of a deal. You cannot use a discount, promo or coupon code with a Trade Up item. Same with Outlet Store items. If you mix Trade Up and Outlet Store items, and sales or regular priced items, then the discount will be taken on them.