Hi there,
Thank you for reaching out to us!
Did you read the following article? It explains how to import venues, organizers and events with examples:
https://theeventscalendar.com/knowledgebase/csv-files-options-and-examples/
In your case, since you’ve already imported the venues, you just have to make sure that the “Event Venue Name” field in your events.csv file matches exactly the Venue Name of the preexisting venue.
I hope this helps! If you have any other questions at all please feel free to let me know and I’d be happy to help as best I can!
Cheers,
Patricia