Without knowing the students' usernames on Wikipedia, you won't be able to grade them.
Create a page for the course on Wikipedia before the term starts. Make sure all students enroll the course page.
Once all students have signed the list, you can come back later and click on "user contributions" (in the menu bar on the left hand side of your browser screen) to review all of the student's activities on Wikipedia
2. Be specific about your expectations
Being specific about what you expect your students to do is crucial for grading. As an example: The assignment for the students could be to add a minimum of 3 new sections to an existing article. Students could also be asked to add a minimum of 8 references to an existing article that lacks the appropriate sourcing, etc.
Note: Please do not grade students based on what stays in Wikipedia. There are many factors that may contribute to a student’s content not remaining in Wikipedia, and if students feel they must fight to control an article for the sake of their grade, this may create conflict with other editors. Remember: Wikipedia editing is a collaborative writing environment that is driven by verifiability, noteworthiness and neutral point of view – all of which have created challenges for students. Additionally, writing for an encyclopedia is different than writing a typical student persuasive paper.
3. Break your Wikipedia assignment into key milestones
Based on experience of many educators, a milestone approach to Wikipedia assignments has proven to be useful to both assessing performance, completing the assignment and grading student contribution.
Additionally, it allows students and Wikipedia editors to engage together in the unique peer editing and collaboration process found on Wikipedia.