When you view an archived page, the date and time of the page is added to the title (so you can see which version you are editing), and there is a special button at the bottom of the page, Replace current which if clicked will cause the current page to be replaced by the page you are viewing (the previously current page is saved in the archive).

If you do not wish to replace the current page, use your Browser’s Back button (or the Back button at the top of the page) to return to the History listing.