It depends on where you have uploaded your site files and how are you trying to access them. If you have added a domain and uploaded the files under /home/user/public_html directory, you will not be able to access the domain via IP. As by default IP address is used as shared one and the document root for it is as /var/www/html
If you see an Apache page while accessing your site using domain name, check the document root in httpd.conf file for the domain.
If you wish to view your site using the IP address, you need to remove the default VirtualHost entry for the IP with the domains Virtual entry.
This may sound confusing but it is difficult to explain all these things rather than practically doing it.
