I can't think of a way to add a train to the bottom of a wedding dress without it looking like an after thought. The train is usually cut with the back of the dress and of the same fabric. The only fabric you might be able to use would be lace, and I don't believe that would look nice just added to the bottom. It might work to add it from the waistline, but you would probably need toches of it elsewhere on the gown. Good luck!