If you are allowed to edit pages in this Site (and, by default, you are), simply click on edit button at the bottom of the page. This will open an editor.
To create a link to a new page, use syntax: [[[new page name]]] or [[[new page name | text to display]]]. Follow the link to create a new page and instantly edit it!
Creating and editing pages is easy and there are many options that let you to create powerful sites!
Please visit Documentation pages to learn more.