How do I generate a report of the participants?

The ‘Participants’ tab under events gives you the option of downloading a report. By directly generating a report from events itself, you are no longer dependent on the general reporting which requires extra filtering.
A direct download button provides quick insight into the status of participation.

From the 'Participants' tab, you can start the download and it will be immediately downloaded as a CSV file. It is not necessary to wait for the e-mail. 

If you can't see the download button, then this is probably due to your assigned permissions. You can then contact the administrator(s) of the academy and ask if they can grant you permission to download participant data for internal events.