If you have an application that uses TextEdit, and you want to modify the application so it uses MLTE instead of TextEdit, you should get the Multilingual Text Engine Software Developer's Kit (SDK). The MLTE SDK is available from the developer's website:
http://developer.apple.com/sdk
The TEtoMLTESample folder in the MLTE SDK contains a project file named TEtoMLTE.proj. When you open that project, you will find the folders TESources and MLTE Sources. You should compare the C++ code in one folder with the comparable code in the other folder. For example, compare TESample.cp with MLTESample.cp. The comments in the file that uses MLTE describe the changes necessary to use MLTE instead of TextEdit.