You add a socket to your skeletal mesh (hand in this instance) then you can swap out various assets as outlined here: https://docs.unrealengine.com/latest/INT/Engine/Content/Types/SkeletalMeshes/Sockets/index.html
You add a socket to your skeletal mesh (hand in this instance) then you can swap out various assets as outlined here: https://docs.unrealengine.com/latest/INT/Engine/Content/Types/SkeletalMeshes/Sockets/index.html