Im not sure about the swift3d ,
but if you have the folder with the texture (.jpg) and the .png (mdf) then you have your model.
you wont be able to view the model though until you drag a spin3d into your presentation.
after you do that you should see a big gear on your screen.
if you dont have the properties inspector open for spin 3d do so in the window menu i believe, i have mine nested with the
regular properties inspector.in the spin3d inspector upper left theres a menu says model with a tab hit the tab , you should now see your model name.select it , you wont see it until you click the big red button to the right on mouse over it says live preview click it .you should see your model skinned already. above the red button theres 2 other buttons ones wire frame and other is textured.if im explaining the
obvious to you im sorry but id rather cover it than you not know.let me know if you get that to work then we can move on from there ok.
as i said though im not sure about the swift importer or if it has a conflict with spin3d. hopefully one of the fine programmers here can answer that one for you.