Create an account on the wiki, go to the #wiki channel on the Fabric Discord, and ping the Wiki Admin role with your wiki username and state that you request wiki editing access.
Search for the page name you want to create, when not found click on the link on:
…you can create or edit the page :a_new_page, named after your query.
or, just type the URL in your browser, for example to create a page named a_new_page
under tutorial
https://fabricmc.net/wiki/tutorial:a_new_page?do=edit
You also probably want to add the new page to the tutorial sidebar, this is done by editing this page.
https://fabricmc.net/wiki/tutorial:sidebar
[ agenda ] See what is on the current agenda, and what other contributors are currently working on.