Go to File--Import Object--Wavefront OBJ.  In the dialog that comes up, leave everything checked and type in a percentage of figure height for the prop.  Position and scale it to fit Mike's head.

Now, if you want the prop not to show the scaling, but come in next time as 100%, export the prop as OBJ, checking top option in that dialog.  Leave others checked.  Delete your original and import the new one.  This time, UNCHECK all boxes on the import dialog.  The hat will appear just where you had it.

One more thing to check is the center point.  If it's off, the hat will rotate around a point in space instead of itself.  With it selected, open the Joint Editor.  A green cross should appear somewhere on the screen.  If not visible, type in 0.000 in all the Center Point locations (X,Y &Z), and pick it up off the floor.  Use two ortho views to place it, then close the JE.

Be sure to parent it to Mike's head.  Apply the texture in the MAT room, and then save it to the library as a smart prop.

John