How can I change/modify/delete the options on my popup choice lists?

Popup choice lists are the user-defined lists that you can assign to any field. They are the best way to enforce uniform data entry - useful for data such as country names, job titles, salutations (Mr, Mrs, Dr etc.) and so on. If you want to modify or delete items from a list, choose Lists from the Setup menu. You'll see a list of your list names; double-click on the one you want to modify.