How to create a new page
The simplest way to create a new page is to first create a link pointing to the new page on an existing page. You do this by editing an existing page and typing:
[[Name of the new page]]
in the appropriate spot. The square brackets indicate that their contents are a link to another page. Once you've submitted this change the page you edited will show a red link to the new page. (Red because it doesn't exist yet.)
Click the red link and you will be allowed to add content to the new page.
For lots of detailed information on editing see the Wikimedia User's Guide