How to add a new skinned mesh to seleton

I need to add cape to horse. But unfortunately I could not find the instructions for this in the documentation. Cape already skinned to horse skeleton. I place horse on scene, add cape to the root of horse object (not bone), so mantle and horse located on same places in hierarchy, on cape in skinned mesh renderer component I set as root bone the root bone of horse skeleton. But horse skeleton does not affect on cape. And cape skeleton (*it saved by default from 3ds max, i also tryed to import just mesh whis skin without skeleton, that i deleted from exported file*) continues to affect the cape. By the way. Does I need save skeleton on cape when i exporting it from 3d editor? Sorry for my english.