To add an item to cart, in your account on the right side, click on view Rewards catalog,
This would take you to a new page, which looks like the below. You may search for the item you're looking to add.
Select an item and click on add to cart, and the item would be added to your cart provided you have the points for the item.
You may checkout once you've added all the items needed.
Fill in your contact and shipping info, agree to T&C and click submit order.
You should receive your order within 2 weeks.