There are 3 ways to add your order to a party before checking out.
You can go to the Party URL provided by the consultant, click "Shop Now", and anything you add to your order will be applied to the party.
The other way is to go to the consultant's store where the party was created, add the items you want for your order, go to your shopping cart BEFORE checking out and you will have an option to select a party you want your order to be applied to.
If you already submitted your order you can log into your account and go to "Purchases" in order to update your order to a party. As long as the order was purchased after the Party Start Date and before the Party End Date then this option will be available.
Customer Service can also update orders to parties but must receive a ticket, phone call, or text message from the person who placed the order.