#Edit in Modelling Software
You should position the skeletal mesh in your modelling software so that where you want it to attach is at the origin
So for a skeletal mesh sword for example, position the mesh so the origin is where you want it to attach to the hand of another skeletal mesh
So the origin of the sword would be around the middle of its hand-grip.
#Previewing Skeletal Meshes Attached to Other Skeletal Meshes
You can always preview the mesh by dragging the skeletal mesh into the socket of the other skeletal mesh in Persona, and then move it around until it is precisely where you want it