At the moment, Apache has no way of knowing about the new installation.
sudo vi /etc/apache2/sites-available/dokuwiki.conf
…and populate that file with:
ServerName dokuwiki.example.com DocumentRoot /var/www/html/dokuwiki AllowOverride All Require all denied Order allow,deny Deny from all ErrorLog /var/log/apache2/dokuwiki_error.log CustomLog /var/log/apache2/dokuwiki_access.log combined
NOTE: If a domain is being used, ensure to change the ServerName option.
Save and close the file.