if you would look up in the manual:

ent_animate(ENTITY* entity,STRING* scene,var percent,var mode)

String* scene reffers to the name of your scene.
If you create frames in MED you can name them. Such as walk1 walk2 walk3 etc.
That name without number is the scene string you have to use between quotes (as string is defined)
For bones I'm not sure. In manual, it says kinda that you should use ANM_ADD to add animations from precalled ent_anim functions. I think in some AUM there was a tutorial about this....? Just remeber I saw one somewhere.

Cheers!