I will assume you have installed a Linux distribution in VirtualBox, to enable the shared folders and clipboard you have to follow these steps:
1- Open a terminal
2- apt-get update
3- apt-get upgrade
4- apt-get install build-essential module-assistant
5- m-a prepare
6- in VirtualBox menu bar choose 'devices -> Install Guest Additions'
7- Go to the terminal and run 'mount /media/cdrom'
8- run 'sh /media/cdrom/VBoxLinuxAdditions.run' and follow the instructions.
Notes:
- If you get errors after step 6, reboot your Linux and continue in step 6.
- You may need root access to run some commands.
After these steps you should be able to share folders and clipboard, you may need to reboot after step 8.
