How to install data-share area on VisualBox 4

To share folders from windows host, We must install VBoxLinuxAdditions to be able to share my folders using vboxfs.
So, when Virtuabox Addons iso mounted :

1.$ sudo mount -o loop VBoxGuestAdditions.iso VBoxGuestAdditions/ or use UI to select VBoxGuestAdditions.iso ;

2. mount /dev/cdrom /mnt/cdrom ;

3.install linux kernel and kernel-headers

    apt-get install linux-source

    apt-get install linux-headers-$(uname -r)

4.run /mnt/cdrom/VBoxLinuxAdditions.run

5.reboot system and run command: mount -t vboxsf shareNode /mnt/share

Just for references, both questions are answered in my howtos:
Howto: Install Linux Guest Additions + Xorg config
Howto: Use Shared Folders