First, create a new VM with 50GB HDD space (you need a lot for the e-mails even though it might not appear like that). Ideally you have the majority of the e-mails on a different sizable partition or SAN.
Do a basic install of CentOS 6.3. Make sure to give a fixed IP address and a proper network configuration during the installation.
# install/update the system, prepare required files
yum -y update
yum -y install wget setuptool system-config-network system-config-firewall ntsysv nscd perl nc sudo sysstat
setup # disable services iptables, sendmail
service iptables stop
service sendmail stop
wget http://files2.zimbra.com/downloads/8.0.0_GA/zcs-8.0.0_GA_5434.RHEL6_64.20120907144639.tgz
tar -xf zcs-8.0.0_GA_5434.RHEL6_64.20120907144639.tgz
vi /etc/hosts
#add ip fqdn
# VMware tools installation. mount your drive!
mkdir /mnt/cdrom
mount /dev/cdrom /mnt/cdrom
cd /tmp
tar -xvf /mnt/cdrom/VMwareTools*.tar.gz
cd vmware-tools-distrib
./vmware-install.pl
# now lets start the Zimbra installation
cd
cd zcs-8.0.0_GA_5434.RHEL6_64.20120907144639
./install.sh --platform-override
su zimbra
zmcontrol status
# Open Firewall ports:
Remote Queue Manager 22
Postfix 25
HTTP 80
POP3 110
IMAP 143
LDAP 389
HTTPS 443
Mailboxd IMAP SSL 993
Mailboxd POP SSL 995
Mailboxd LMTP 7025