It's very similar to the configuration tool provided by .LRN's new-portal package, and should be self-explanatory. Similar restrictions apply, in particular you con't remove a page that has elements bound to it.
However, unlike new-portal, you may change the layout of a page even if it contains elements. If you change to a layout with fewer columns, elements that were on columns that don't exist in the new layout are placed on the rightmost column. If you change to a layout with additional columns, those columns will initially be blank.
When you create a new page, you must provide a human-readable page name, which can be localized. The page will be created with a default URL snippet derived from the human-readable name. The name is converted to lower case, spaces converted to "-", and non-alphanumeric characters other than "-" removed. Its theme will be blank (in other words, will inherit the pageset theme), and the page will initally have two columns.
After the page has been created, you can edit the page's URL snippet (the character restrictions described above will be enforced, and URL snippets must be unique within a given pageset), theme, and page layout template.