All wiki pages or articles (both words describe here the same thing) are created by following a link that does not exist yet. You will learn here how to create such link and what to consider before creating a new page.
Search for an existing article
Before creating a page, be sure it does not exist yet on the wiki. Search for it in the search bar (shortcut is /). If the page already exist but you think people might search for it under a different name create a redirect. Consider also broadening you search to other articles that might include your subject as a section. It is often better to contribute to an existing article, and when a section becomes too big, move it to its own page.
Create a page
The best way to create a new page is to follow a red link from an existing page referring to your subject. Or creating this red link [[Name of the new page]] on that page. It's the best way to start because your article will already be linked to another and thus easier to find. The other way is to search for the wanted page in the search bar, you will be proposed to create it.
Namespaces
Namespaces on Mediawiki (the sofware that powers this wiki) allow for separation of content pages and administration pages. The page you are consulting right now is in the <tt>Help:</tt> namespace, which contains pages providing help using the wiki. Pages with no prefix are in the main namespace and are the core articles of the wiki! As a usual rule, be a bit more cautious when creating things outside the main space, and avoid editing other people <tt>User:</tt> page. Also if you want to create a page related to you, your projects, drafts or with you opinions, create them as subpages of your userpage! For example : User:Côme/Draft.