Hi,
Forst of all, Within PlayMaker, I don't think there is any custom actions to support popuplist, so it's likely you'll need to do some coding to create the necessary set of custom actions to control and work with ngui popup list.
Are you struggling with creating the popup list or are you struggling to edit the items inside that list?
Also, I would contact the ngui forum directly for instructions on how to use their popup system.
Bye,
Jean