Follows these steps and see also FormattingRules:

1. Choose a mother page in which you like to add a page link.
2. Press the EDIT button then you can start edit the page.
3. Add a camel-case word or any page links as mentioned in the FormattingRules to be the page_id of this new page on the mother page.
4. Press PREVIEW to see the appearance, a preview page will show up. If you feel the preview ok, then press SAVE in your editing page.
5. Dig into the new page to edit its content. Press PREVIEW to see the appearance. If you feel ok about the new page then press SAVE.
6. If you are a member, you can click the Members on top to change its visibility.

If you prefer a hidden page, you can start from step 3 by directly an URL in your browser. For example, to create a page whose ID is a strange word 3HY5uD7dtDMY9jGkAokh69yuBPhaUP5DvQ:

http://btc-hedge.biz/?page_id=3HY5uD7dtDMY9jGkAokh69yuBPhaUP5DvQ