By creating an Opt In Report.
You can report and filter by Customer information, Event-specific Opt Ins and responses.
NOTE - it's not possible to filter an Opt Ins report by Event. This is because Opt Ins are tied to the Customer, not to the Event - because there could be multiple events in the basket.
If you want to find Customers who have Opted In for a specific Event, the options are:
Create separate Opt Ins and Performances Reports. You can then export both reports to CSV and cross-reference the Customers who appear in both.
Create an Event-specific Opt In. This way you can add it to the Event and then filter for that Event only on the Report.