If you haven't uploaded anything, then this page looks about right. It is a placeholder for a future website. Once you upload a website 9to the public_html directory) and remove/replace the current index.[html|php] file then it will display your page and not the placeholder page.
Also if you have a lot of websites and don't want to remove index.html each time you can change priority in this files for whole server: /etc/httpd/conf/extra/httpd-directoryindex.conf
/etc/nginx/nginx-directoryindex.conf
and put index.php on first place like: DirectoryIndex index.php index.html index.htm index.shtml index.phtml
and protect file from overwriting with chattr +i
Or better modify appropriate template in: /usr/local/directadmin/custombuild/custom
To be exact, in that case it should be this: /usr/local/directadmin/custombuild/custom/ap2/conf/extra/httpd-directoryindex.conf
This is only for normal Apache, for nGinx or Litespeed is probably different.