OK, I have a train model in obj format. However, it imports as one large object into A:M and I cannot select anything individually in order to add bones for such like making the wheels turn. Any ideas?
Notice the part I've bold-faced.
As mentioned above, a good tactic for mechanical things is to separate the parts in the original program and import each as a separate prop model. Then in the chor you can constrain them together and animate the parts that need to animate.
It IS possible also to import Polygonal models directly into an A:M model window but most polygonal models are poor candidates for conversion to splines. It's free to try, none-the-less.