Hi there Thomas,
Thanks for getting in touch with us, and sorry for the confusion here.
Event Aggregator is a service built into The Events Calendar. This means there’s no separate plugin you need to download for this, but a feature you activate by configuring a valid Event Aggregator license key.
So just go ahead and update The Events Calendar to version 4.3 from your WordPress site. Once that’s done configure your Aggregator license key (WP-Admin > Events > Settings > Licenses) and save changes. This will enable you to perform imports from WP-Admin > Events > Imports. Also, be sure to check out this article covering the basics → New User Primer: Event Aggregator.
Please let me know if the above helps,
Best,
Nico