On the Lists screen, tap the List Settings gear button next to the list for which you want to edit categories.
Tap on Category Group.
Tap on the info button to modify the built-in Grocery group, or tap on Create a new group if you plan to create multiple groups (e.g., one group for each store where you shop).
Add categories by tapping the Add Categories button.
Reorder categories by using the drag control to the right of each category.
Remove a category by tapping the red circle next to the category name.
Rename a category or choose a new category icon by tapping the category name.
Tap Done to apply your changes.