Recording who attended an event is as simple as a click.
You must be an administrator to record attendance.
The attendance module must be enabled in your group settings.
See Updating a group.
Click on the event in the event list. Next to each member in the member availability details is an Attended checkbox. Tick or untick as necessary, all updates are automatically saved.
Clicking on the 'Paste Attendees' link, a box appears where you can paste the names.