1- Create the page in the new language
On the page you want to translate, change the language prefix (xxx.wikipedia.org) to your language's prefix. This will bring you to a blank page and Wikipedia will ask you if you want to edit it. If you don't know your language's prefix, find it by going to www.wikipedia.org where all the languages are listed.
For example, if you want to translate the article en.wikipedia.org/wiki/Stack_Exchange_Network to Japanese, go to ja.wikipedia.org/wiki/Stack_Exchange_Network and find the link to edit the page.
However, it can most often be that the translation of the article has also a translated name. For example, if you translate the page square into french, you would not create the page fr.wikipedia.org/wiki/square but the page https://fr.wikipedia.org/wiki/Carr%C3%A9
2- Link the new created page to the other languages
a. Once you have created the article in your language, let's say fr.wikipedia.org/wiki/Carré go to the page in an old language, e.g., english en.wikipedio.org/Square and there click on Edit Links under the languages names
b. Now, a site opens with a frame called just wikipedia and Edit on top of the languages: click again on this "Edit" link.
c. Finally you end up in the linking form. There you have to fill the fields Site ID with the language wiki id, for example, in our case is frwiki for the french wikipedia page. And fill the field Sitelink just with the name (not the full address!) of your new translated page, in our case, with Carré.
d. Click Set the sitelink and your translated page should be accessible from the main page of the other languages in the languages links.
Best Answer
Many citations use the Cite web template, or any of the other Citation Style 1 templates. All of these have an
archive-url,archive-dateandurl-statusparameter. Simply add these to the citation.archive-urlis of course the url to the Wayback Machine (or another archival website)archive-dateshould be set to the date the webpage was archived, preferably in the same date formatting as the existingdateparameter.url-statusshould be set to eitherdead,live,unfit, orusurped. If the original URL is still available, set it tolive, otherwise, set it todead. This will change which of the links (archive-urlorurl) is linked to first in the rendered citation. If the original link is no longer suitable at all (perhaps because the someone else owns that domain now) set it tounfitorusurped, which will prevent the original link from rendering at all.For the Citation you mentioned, you can see in this diff how I've done this. Note:
url-statusused to bedead-url, which has been deprecated. My edit from July 2018 has been updated in September 2019, see this diff.