I'm honestly not sure! It used to be that you could click on the logo in the main
Facebook Developer Area
for your app and update it there. However, that ability is gone, and I'm not seeing where it's done now.
We are looking, but we can't even find a way to do it for our own app.. or see what we have set. Facebook overhauled their app admin area recently, and this may be a missing feature.. though it's a big one.
We'll let you know what we find out, and sorry for the inconvenience. Maybe we're just overlooking the obvious though, so if you find it, let us know!
Thanks,
Alex