The guide you mention doesn’t say to create a file /etc/apache2/conf.d/example.conf
I presume you’re therefore trying to run this only on a particular hostname, and having other requests go elsewhere? In which case, you need to have a ServerName setting in there so that Apache can match requests to this.
If you just want all requests to go to Xibo, then go back to the guide and follow the instructions there (which tell you to edit /etc/apache2/sites-available/000-default.conf