How to manage an event assigned to a group?

Click on the right arrow button across the group’s name as shown below.

On the Content tab, click on the Manage button across the Event content. 

On the Manage by Users tab, you can see the statistics of the events like, the users registered to the event and the number of users who attended the event.

On the Manage by Session tab, you can see the list of users and to which of the sessions they have been registered to and their status