Default configuration file: /etc/apache2/sites-available/
You will need to create a vhost in this directory, with the file ending in .conf.
For example:
/etc/apache2/sites-available/example.com.conf
<VirtualHost *:80>
ServerAdmin [email protected]
ServerName example.com
ServerAlias www.example.com
DocumentRoot /var/www/vhosts/example.com
<Directory /var/www/vhosts/example.com>
Options Indexes FollowSymLinks
AllowOverride None
Order allow,deny
Allow from all
</Directory>
ErrorLog logs/example.com-error_log
CustomLog logs/example.com-access_log common
</VirtualHost>
Once the vhost has been created you will need to enable the vhost using a sym-link and then reload apache for the configuration to take effect:
sudo a2ensite example.com.conf
service httpd reload