Guide on adding a new model, animation, and creature to HoMMV

Please help a clumsy person; my model just won't appear no matter what I do. I only made a few minor changes to the model in Blender, but then something went wrong, and I can't get the model back into the game. If anyone can help, I would be very grateful; I'm attaching the FBX file.

I know the problem is probably with the bones, as they got messed up a bit when importing the model into Blender, but I don't know how to fix it.