To Edit Category follow these steps:
If you are using mouse, right click on category to edit.
If you are using touch device, perform select item gesture on category to edit. (see below how to select category using touch)
Category will be selected and bottom app bar will be shown.
Tap on Edit icon.
Category will be opened in edit mode.
Make changes and tap on save button.
How to select category item using touch.
Touch the category with your finger (Do not leave the finger from screen yet).
Swipe the category item down slowly until check mark is completely shown just above the category item.
Category item will be selected and App bar will be opened from bottom.