Step 1. update to last repo
# yum -y install epel-release
# yum -y update
# yum install make gcc kernel-headers kernel-devel perl dkms bzip2
# reboot
Step 2. mount CDROM and install
# mkdir /mnt/cdrom
# mount /dev/cdrom /mnt/cdrom
# cd /mnt/cdrom
# ./VBoxLinuxAdditions.run
# reboot