If you are allowed to edit pages in this Site, simply click on edit button at the bottom of the page. This will open an editor with a toolbar palette with options.
To create a new page, use the Add a new page box to the left. Just type in the name of the page you want to create and click the "new page" to open a brand new page with a toolbar palette with options.
To create a link to a page, use syntax: [[[page name]]] or [[[page name | text to display]]]. Follow the link (which should have a different color if page does not exist) and create a new page and edit it!
Although creating and editing pages is easy, there are a lot more options that allows creating powerful sites. Please visit Documentation pages to learn more.