To Edit Category follow these steps:
Tap on the menu icon located at top left corner.
A screen will slide from left side.
Tap on Category icon, all categories will be shown.
If you are using mouse, right click on category to edit.
If you are using touch device, long press on a category to edit.
A pop-up menu will be shown.
Tap on Edit menu.
Category will be opened in edit mode.
Make changes and tap on save button.