Hey Huw and thanks for getting in touch! I’m glad you’re checking out Events Calendar PRO and I hope it’s a nice fit for your site. 🙂
Great question. ACF fields can certainly be added to the event editing screen. From there, however, you will need to customize the calendar templates to display those ACF fields. We have a Themer’s Guide that walks through the process of overriding the calendar’s templates with your own and that’s the place I would suggest starting for a customization like this.
Does this help answer your question? Please let me know. 🙂
Cheers!
Geoff