# To install Guest additions, go to: 
    # Devices --> Insert Guest Additions CD Image 

# Open Terminal and type in the following: 
cd /media/ 
ls # Find the Guest Addition CD Image directory
cd {Guest Additions CD Image}
sh autorun.sh
sudo reboot 

# When the system reboots, go into full-screen mode: 
    # right control + f 
    # View --> Full-Screen Mode 
# The resulution should now be greater than the default 800x600