This is just an example image of how to use the primitive mirror.






Here you must duplicate the body of your choosing and bring it to the other side of the mirror. Then flip the pose in the opposite direction.

Next duplicate layer with the 3D objects and delete the duplicate body shape that’s in the duplicate layer. Once that’s done go back to the first layer that’s under the duplicate layer and delete the first body and mirror frame. Once you do merge the layer with just the body down an empty layer then erase the part you don’t need.
This is the example down below.




