How do you edit skyrim model with gmax

All of the Skyrim models (or models from games developed by Bethesda Studios in fact) are in the NIF format. To view them, you need to have the NifTools plugins for your 3D program. I only know of plugins for Maya, Blender and 3DS Max, but there may be one for GMax. Also, Skyrim uses a different NIF header that won't load into older tools. Rest assured that the Skyrim modding community is growing rapidly and people are always working on ways to edit every aspect of the game.