There are three ways to start a new page.
1. Use the Add a New Page Box
In every default theme, there is a box labeled Add a new page in the left side bar. Type in the name of the page you want to create and click the button marked new page. You will be taken to the page editor. Type in something and then click save at the bottom of the page editor.
2. Click on a Link
Click on a link leading to an uncreated page - like this one. You will be taken to the uncreated page. Click on the link that says create this page and you will be taken to the page editor. Type in something and then click save at the bottom of the page editor.
3. Edit the Url (Advanced Skill)
In the url box of your browser, edit the url so that it leads to an uncreated page. Then proceed as usual.
Some Notes
The name of the page that you type into the Add a new page box is the url of the page, not necessarily the title. The url and the page title are independent. For more information see : Page title.
TODO : add something on the choose template dialog which appears directly at the creation of the new page