Hey Frank,
Welcome to the forums!
Let’s see if we can get this figured out. First, have you tried uploading a featured image when adding/editing an event? (see screenshot below) It’s typically found on the right-hand side of your edit event screen.

In response to your follow up: First, visit Events > Settings > Display and try some different options to see if you’re able to get your event image displaying properly. If you haven’t already, review our New User Primer. We provide insight on how the plugin works.
You may also want to explore the Themer’s Guide. This is where we give examples and instructions on creating custom templates. Lastly, our Testing for conflicts is a great resource when trying to narrow down conflicts.
I hope this helps answer your question and feel free to respond if you have any additional questions or comments. Thanks for choosing PRO and again, welcome to the forums!