You can display alternative forms only through the special names (insert,update,newculture,filter) in the CMS Desk. On the live site you can display it by Contributions list web part.
Usage of page type alternative form from the documentation:
Live site - using for example the Contributions list web part (see the User contributions chapter for more details).
In the Pages application to replace the default forms for adding or editing pages (after clicking New or on the page's Form tab).
In the Pages application on the Listing to allow editors to use custom fields of a specific page type when filtering the listing.