Unless you own a negative having the same size of the image you want to get, you need an enlarged negative to make old process prints. I have never tried the conventional way, that is by making use of sheet films and an enlarger, so I can only tell you that a computer is a convenient method to produce contact negatives. The basic steps are: scanning the negative, using an image manipulating software to create a digital negative of the desired size, and printing out the image onto a trasparency film.