Sounds like it is an older Designer I. You have to have some software to create floppy disks that the sewing machine can read. The disks are formatted with a proprietary folder structure. You cannot just drag and drop the embroidery file. The Viking dealer should be able to get you a copy of 3D Organizer which will allow you to send a single design to the Floppy. You will have to purchase a floppy drive for your PC if you don't already have one.
I have an older Designer I and love it. In addition to the embroidery, it will sew thru ANYTHING.