To manage Idea categories, navigate to the Ideas tab, and click on "Manage Categories"(shown below). By default, every member of a project or team can edit these categories. In premium projects and teams, admins can set permissions.
Admin tools are a Premium feature, to see all benefits of upgrading your Project to Premium, click here.
This window will open (shown below), here you can search for categories, add new categories, edit categories, and delete categories. Note, however, that if you delete a category, all Ideas that have been assigned to it will be re-assigned to the "general" category. General is created by default:
To create a category, type it into the box labelled "Add New Category" and then click "+ Add".
To delete a category, click on the delete button:
Clicking the delete button will prompt this window.
If you still want to delete the category, click on the "OK"'. If you changed your mind, click "Cancel".
Once you have deleted the category, you cannot recover it and any Ideas assigned to it will be assigned to "General".