To add an item to a list, type a new name into the blank box at the top and click "Add new". To rename an item, re-type its name and then click the "Rename" button immediately to its right. To delete an item, click the "Delete" button immediately to its right.

You must be careful. You will not be asked for confirmation of any of your actions. Bearing in mind that each item in the list is represented internally by a unique number, care must be taken when deleting items. If you delete an item, everything that was associated with it will not be associated with anything in the list any more. Even if you create a new item with the same name, it'll have a new unique number, and the system will not treat it as the same thing.

It's worth noting that you can only rename one thing at a time. If you attempt to rename several items, only the one nearest the "Rename" button that you clicked will actually be changed.