After installing apache in CentOS it would go to Apache 2 Test Page.
To locate this directory you need to go to /var/www/
In this directory you can create your file which you needs to run.
To set up Virtual Host navigate to /etc/httpd/conf/httpd.conf file
Open the file in gedit or editor of your preference.
Add the lines below
<VirtualHost *:80> DocumentRoot /var/www/sample/ ServerName virtualhost1 </VirtualHost>
The document root points out to sample older in www directory
The server name is virtual host name you type in URL
You should also add the code in /etc/hosts file
127.0.0.1 virtualhost1
Once this is done dont forget to restart apache server in terminal by typing service httpd.restart
Now you are ready to go now.Open the browser and type http://virtualhost1/
Cheers!!!