yep, first X needs configured if it isnt already
in linux the graphical part your used to is set up as a server-client and its modular, and its called X, several GUI or graphical user interfaces are available unlike windows, which run on top of X as clients.Most common ones are GNOME and KDE, both of which come with most of the software the average person will need.
first off, assuming your looking at a command line prompt(blank screen with a login prompt), try typing startx
if it comes back with an error, its not setup yet
As ROOT: (logged in as root)
type xorgconfig or xf86config, there's two X servers that most distro's use, not sure which one ubuntu uses
you can type part of a command then hit the tab key and it will fill in the rest for you, that way if im off on the syntax for those commands it will fill it in anyway, sometimes they are case sensitive, example may be XF86Config or xfree86config or xorgconfig, it varies
That will run you thru a set of questions about your mouse,keyboard, monitor, and video card........answer the questions and when thats done, try startx again, should be ok after that, if not, your xconfig prob isnt right or your graphics card isnt supported
dunno what window managers ubuntu has, may want to try typing xwmconfig and see if it has a simple little options program to choose one, may not, dont worry if it doesnt
after everything is up and working, you will need to setup a user account, you shouldnt run as root all the time, thats for system changes only, as root try adduser <username> or useradd <username> to set one up