On the “Plan” tab where your meal plan is, there is a “Shop list” link at the top right that will allow you to auto-create a shopping list for the whole week or for a set of dates you specify. If you have recipes in your plan with shopping items, it will automatically pull the shopping items into the grocery list.
You can also pull in meals from a set of dates from within the shopping list, by clicking on the “Add items” link next ot the "My Plan" icon in the "Click to Add" area of the page on the right,