After the initial installation of ubuntu I suggest you play with it
a while, setting up OS and desktop services to your liking.  This
learning curve will make you more comfortable in the following steps,
as well as prevent you from loosing a lot of work if you do something to
blow it out of the water and need to re-install.

I would first get the physical desktop setup complete as to monitor
discover/location/size.  If it turns out you need/want propietary
drivers for your video card, now is the time to do it.  When building
my last system, I didn't try that step till 2 days into the install
and completely bricked the system by trying to load AMD Cataylst from
the ADM site.  Learn from my mistakes!

Open "System Settings", either from the 'gear' at top right corner
of desktop, or the 'gear/wrench' icon in launcher at left of screen.

  click Hardware:Displays

and follow the directions. Be sure to get the mouse moving between
monitors as expected, and the resolutions correct.  I suggest testing
these settings by doing a shutdown & repower of ubuntu after you believe
they are correct to insure all is well.  The BIOS sometimes gets in the
way of this, you might have to play with BIOS settings as to which GPU
is used during boot, etc.

After the above is finished to your satisfaction, again Open "System Settings",

  click Appearance

Within the 'Look' tab, set your desktop to your likeing.

  click the 'Behaviour' tab

I suggest you "Enable workspaces" and "Add show desktop icon to the launcher"
I like the "In the window's title bar" option, don't auto-hide launcher for now...

Visit the "Brightness & Lock" tab and set as desired.  I have encountered
issues with some monitors not waking properly and had to disable screen turn-off.