I am trying to key-frame animate a rigged character purchased from TurboSquid. I haven't been able to find any online tutorials or videos about this. There are ton of tutorials on how to rig a character you have made, but not many on how to animate an existing rigged character. Any help would be appreciated.

For some reason, when I go to rotate a joint, it makes a copy of the model rather than just manipulating the one existing.

In the screen shot, I'm trying to animate the skeleton to wave. I select a point on the timeline, rotate around the joint and it makes a second arm instead of rotating the existing.

If I can figure out how to properly manipulate the rigged character, than key frame animation is fairly simply.