Embroidery software unobtainable due to usb serial port issue

I have a bernina artista 180 embroidery machine. I downloaded the artlink software onto my laptop and purchased a USB serial port adapter cable. I'm able to open the designs from my cd on my laptop but am getting an error message "serial port engaged". Then the screen comes up to select the com port? I'm just using a USB port. When I ignore that my design pops up again but there's a connection failure and the design can't be moved from my laptop to my machine. What should I do?