Since you have only one public address, named based virtual hosting is the way to go.
for that open /etc/httpd/conf/httpd.conf (apache configuration file) in your favourate editor and edit the following lines...
NamedVirtualHost 211.118.126.11:80
# where 211.118.126.11 is your public IP address
<VirtualHost 211.118.126.11:80>
...
...
ServerAlias
www.xyz.com
...
</VirtualHost>
<VirtualHost 211.118.126.11:80>
...
...
ServerAlias
www.abc.com
...
</VirtualHost>
You can give any number of virtual host directives. The ServerAlias points to the site you want to host. That way you can host multiple sites.
Frankly speaking, there is much much more to apache configuration than what I have writen. It is advisable to really read the excellent manual that comes with the distro.
