If you had a chance to setup monitor settings during your install, you might be able to login at the prompt and type 'startx' to start the GUI. If that goes crazy, you can hit ctrl-alt-backspace to exit it. Then it's a matter of setting up your GUI.
If this is the case, then as root, you need to type 'su' and the root passord you created during the install. Then:
this is the simplest way to setup your gui, if it's not the prettiest way to do so.
Naturally, this is assuming you installed with the "typical" or similar option. A minimal install wont include the GUI, and if you haven't put much time into the OS, the best way for newbies to succeed is to reinstall. That's a tough recommendation, as a skilled Linux user won't spend a second considering a reinstall. There's just too much information available to force that option, unlike windows.