multiple applications setup

Hi Folks,
I am about to built a codeigniter website with a set of multiple applications .
Regarding the directory layout I would like to follow codeigniter standards https://ellislab.com/codeigniter/user-gu..._apps.html and organize the applications accordingly.
/codeigniter_root/application/appone
/codeigniter_root/application/apptwo
/codeigniter_root/application/appthree
What I am missing in the user guide is how should we manage the access to multiple applications.
The user guide mention only access to one specific application by defining “application_folder” in the config.php but the point is the access the application by adding application name as a suffix to the domain-name ex :
http://domain-name/appone , http://domain-name/apptwo , http://domain-name/appthree and I don't see this explanation in the document.
Could anybody point me to right direction?