So first the basics of setting up the Pi are as follows.
Get a Micro SD card
Choose your flavor of linux from the downloads page of the Raspberry Pi website
And use the installation guide link from the downloads page to write it to your Micro SD card http://www.raspberrypi.org/documentation/installation/installing-images/README.md
Find and connect these into your Pi:
5V 1A Micro USB wall charger
Monitor with HDMI input
Connect all of the hardware up to the Raspberry Pi and then once this is done connect the power cable up to the Pi. The monitor should come up with the first time login loading all the hardware drivers and then take you to the config menu of the Pi. In this section you can mess with it as you choose but make sure to select make the entirety of the Micro SD card available to the operating system. Once this is done select finish and wait as the Pi reboots. Once the command line has finished loading and checking everything you can log in off the command line.
The default username is: pi
The default password is: raspberry
Once you enter this in type into the command line startx to load the gui (graphical user interface)