I purchased two dell monitors and a stand to hold them together and it looks great.  However, one monitor is plugged into the computer with the normal cable.  The other monitor needs to use a USB port as I only have one port for the monitor.  I can get the normal cabled monitor to work just fine.  The USB cable monitor will not work.  The monitor is fine.  How can I get the one plugged in with th USB cable to work and then how can I get them to work together so I can drag files and such back and forth?

Thanks for your help