How can you tell who wrote a particular article on Wikipedia?

I'm answering some criteria about a particular article on wikipedia, but I don't know who wrote it, is there a way to tell?

Unfortunately many people contribute to wikipedia's content and articles. You can however to go the history tab of any article, top of the page, and it will let you know which users contributed what content or any modifications made.

Go to the last page of edits and the last one on the bottom is the person who created it.

it should say at the top this article by ____ or something like that

You can't

At the top of every Wikipedia article, there are a series of tabs, and one of them reads "history". By clicking on that tab, you will be able to see every person who has edited that particular article, and every time that they edited it. To find out who created that article, click "earliest" where it says (Latest | Earliest) in the first line before the logs.

You use the tab that says "History" in dark blue at the top of the respective page. There you see a list of some but not necessarily all of the edits done to the page and the editors who made those edits. Remember that Wikipedia administrators have an oversight option which allows them to wipe edits off the face of the Earth without anyone noticing, so even the "History" list of a given Wikipedia page might not show all the users who edited that page. It is misleading sometimes.