This Wiki is organized as a set of "spaces".  A space is the top level of the organizational hierarchy.  Below a space is a hierarchical structure of pages. 

The preferred organization within a space is to make all pages children of the "Home" page. Every space has a "Home" page by default, and by default this is what a user will see when loading a space.  The system will automatically show the children at the bottom of the "Home" page.  They will be not as conveniently accessed if they are siblings of the "Home" page.

When adding a page by clicking the "Add Page" link, you will be adding a page as a child to the page you are currently looking at.  So, if you want to add a child page to a space's "Home", just load the "Home" and click "Add Page".