First, log in to your 3CX web client, then click Admin at the bottom, then M. Console (management console).
On the left, click "Reports"
Then, find the date AFTER the day of the call you want to listen to. Each report is generated at 5am for all calls within the previous 24 hours, so the date is off by 1 day.
Click "View" and it will open up a new window.
Then, find the call in question. On the right side, click the blue button in the "Play" column to download the recording.