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 red link
The best way to create a new page is to follow a red link from an existing page referring to your subject. Or creating a red link [[Name of the page]] on that page. It's the best way to start because your article will not be an orphan and thus will be easier to find.