On the Lists screen, tap the List Settings gear button next to the list for which you want to edit categories.
Tap the Categories row.
(Note: If category sets are enabled for this list, tap the Category Sets row and then tap on the category set you wish to edit).
Add a category by tapping the Add Category 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.