You can edit your order by simply adding your forgotten items to your cart before the order deadline. You will not get another email confirmation but whatever changes you make will automatically be saved.
Here is a list of order deadlines by delivery route:
High Springs, Gainesville, Ocala, Brooksville, Tampa, Brandon, Bradenton, Clearwater, Largo: Every Saturday at 11:59 pm
Jacksonville: Every other Saturday at 11:59 pm
Tallahassee and Monticello: Every other Saturday at 11:59 pm
At the top of the page it will say how much time you have left to order, if it says "You can place your order in __ days" then you have missed the deadline and ordering for that location is closed.
You can review old orders by going to "Account" and selecting "Order History" from the drop down menu