I don’t know if there’s an official procedure for it. In the past I’ve just gone to the previous comp page and copied and pasted things onto the new page. If there’s no link yet for the (not-yet-existing) competition page, you can add it to “Competition News” first.
Edited to add: If you try to edit the wiki and it asks you for a magic word or something like that, it’s probably one of the words from this page: Xyzzy - IFWiki
You are welcome to use or adapt the attached script if you want. For a little while I was using it to scrape IFDB to make ifwiki pages. (The script is saved as a text file here because otherwise the forum won’t let me upload it.) I haven’t tried it recently, so can’t guarantee that it works. ifwiki.txt (34.3 KB)
I’m not going to try to answer that, but you might find this thread interesting: What would you like to see on IFWiki? (Survey)