I don't think there was any additional work besides attending the weekly meetings last fall. At many of the meetings, presentations of research currently being done are given, so the students get an idea of what might interest them. I don't know specifically about CS, but my D said they run the gamut of disciplines. At the end of the semester, the students are asked to list their preferences, then they are matched with the professor doing the research.
The second semester is when there will be more of a time commitment. Depending on what they're doing it could be several hours per week. Plus, there is a project to be presented at the end.