I would think that you might first want to read:
"OpenEdge Development: Internationalizing Applications"
I would also think that you would want to be thinking in terms of unicode.
One big problem that I recall having working with being able to enter Chinese characters was finding a terminal emulator that supported them. If you're using Windows you also need to install or enable a bunch of stuff from MS to get it to work properly.
You also need to think long and hard about the implications of having mixed character sets in your data. If you are going to allow that things can get very, very complicated.