I am trying to attach the animation rig controls of the autorig tool to an FBX imported characted from Mixamo, but I have no idea how to approach this.

Also I can't generate a Mocap Rig from the designated Button on the animation rig node after creating a fresh autorig. It tells me to select a skeleton, but which skeleton should I select? There is none, just the individual nodes for spine, left_arm etc.

I think the autorig tool currently lacks proper documentation covering more than just the default procedure.