Need help configuring dual monitors - ML10 Gen9

[clarkleach]

I just installed Debian 8.7.1 on a brand new ProLiant ML10 Gen9 which I am going to use as a workstation.  I have attached two monitors via the two Display Ports.  Everything works except I can't get the monitors configured as an extended desktop.  It's as if the OS thinks there is only one monitor attached.  Are there any non-free drivers that I need to install to make this magic happen?  I have managed to configure extended desktops in the past in Debian Jessie. While not as simple and elegant as the Windoze solution, it is not rocket science - which leads me to believe I have missed something in the commissioning of this system.  Help!?