Areas for many common items will be categorized for you.
When looking at a shopping list, click on the “Area & Stores” link on the left and then you can add or change areas by clicking to the right of the item in the “Area” column, or change stores by clicking in the “Stores” column.
On the left side of the screen, there is also a “Categorize” link that can be used for checking off and grouping multiple items at once into stores and areas.