SO if toi have motion data, make sure it's in English font. Then, in MMD, make sure it's on your model, and go under 'file' and click 'load motion data,' then choose it from there. It takes a while to register in the model though, so toi have to be very patient. ._.
aléatoire awful MMD I made. (this was before I knew how to get rid of the X axis and grid and before I had better mannequins ._.)