There are several ways to start a new page. These can vary, based on the type of page started, as well as the wiki and the namespace it is in.
If you search for a page that doesn't exist (using the search box and “🔍” button at the upper right of the page), then the following line will appear:
Create the page "[Proposed Title]" on this wiki!
It will be above any search results should any appear. Simply click on the link to open the new page for editing.
Using the browser address bar to enter a URL (web address) to a new page is another way to start the new page process. Easier still is editing the page name part of a URL for an existing page. Using the URL for the new page displays the default 'no article' message. The default page has the usual Edit this page link, which can be used to begin adding content.
The Community portal on all wikis has a "Start a new article" bullet point by default. Typing in the name of the page and clicking the now blue 'Create page' button will redirect to the default page with the usual Edit this page link, which can be used to begin adding content.
New pages and blank pages
A new page is distinguishable from a blank page: the latter has a page history. Creating a new page is just like editing a blank page, but links to blank pages will not be red.
Categories and category pages are technically separate, and a category can exist without a page. When you open a category page that doesn't exist, you may see that that pages are already in the associated category. The main use of category pages is to put categories within more general categories, as categorizing the category page will categorize the category too. This allows a wiki community to create a hierarchy of categories. Category pages can also be utilized to provide further information on the type of articles contained in the category.
Image files and file pages are also technically separate, but typically a link to a file page will not be red unless the image is missing. File pages are useful for categorizing images, showing license information, and providing a description of the image.