The figure above, gives the top view of the model / character's arm. Make the required corrections to the shape of the model / character you have created, by comparing it with the figure given above. I have avoided modeling all the fingers, since it will be time consuming and repetitive. You can split the knuckle joint using vertices and extrude them in the same way you extruded the thumb, to create the other fingers in 3D Studio MAX ( 3ds max ). By adding more cross-sectional segments along the finger, you can create the joint and more details. Experiment with them as an exercise.

Don't forget to save the scene. You can download the scene here if in case you need it for reference.