apt-get update
3 Install the latest security updates with apt-get upgrade
4 Install required packages with apt-get install build-essential module-assistant
5 Configure your system for building kernel modules by running m-a prepare
6 Click on Install Guest Additions… from the Devices menu, then run mount /media/cdrom
7 Run sh /media/cdrom/VBoxLinuxAdditions.run and follow the instructions on screen