You can edit your order within one hour of initial placement.
Sign into your SMILE account and click on the "Order History" tab.
Here, you will see the order you most recently placed. You can edit this order if the status is still classified as "Quote."
Click the order you're wanting to edit. Once you're on the order details page, click the "Edit" button at the bottom.
Add your desired missing items and check out like normal.
After the order status turns to "Pending" you will no longer be able to edit that order. This happens after 1 hour.