I think when you import models with animations into Godot, they get imported as a scene with an AnimationPlayer in it. I guess you then have to get that node and use it to play animations, using the names you gave them.
If you don’t see any AnimationPlayer in the imported scene, maybe the format you used for your model doesn’t support them (like OBJ). If that’s the case, try another format like GLTF or Collada (DAE).