MediaWiki has a GuidedTour extension which provides interactive tutorials. You can see it by adding a parameter tour=test to the URL, like here. GuidedTour is not yet used on wikisource.org. Read the extension page and especially the section ""Designing a tour"". See this bug report for more information. The technical details on Write_an_on-wiki_tour might be helpful only in case you are also interested in the technology behind. Students are required to read Wikimedia's general instructions first.