There are several ways to use your Dashboard course page to see what your students have done on Wikipedia. Which one to use depends on what exactly you're trying to do:
To see their latest edits, use the Activity tab. This shows a list of the most recent edits made by the students. You can click the timestamp of an edit to view it on Wikipedia, or click the "+/-" icon to see the "diff" of what was added and removed in that edit.
To see the live Wikipedia articles your students have edited, and how each one changed, use the Articles tab of your course page. This lists each article edited, along with approximately how much content your students added. Click the page icon for an article to use the Article Viewer, which will load authorship highlighting information to indicate which text in the latest version of the article was contributed by which student.
To see what an individual student has done, use the Students tab and click on a student. The student details view (Assignments & Exercises) shows which article(s) a student is assigned, which articles they are peer reviewing, which additional articles they've edited, which training modules they've completed, and more. For assigned articles and peer reviews, this includes links to the sandbox pages where they should be compiling bibliographies, drafting content, and submitting reviews.