Well, I'm not 100% sure, but if skeletons are treated as they were in Oblivion and Morrowind (and it seems that they are), then there is no simple way to make them wear armour. Of course, you could put it in their inventory, and after killing them, you could loot it, but the skeleton would not wear it. To make a skeleton wear armour, you would need to create a new skeleton model that has the armour already on. For that you would need 3DSMax or Blender or some other programme like this and some knowledge of rigging.