My users want to add attendees to their calendar events that they add in Salesforce Lightning. I'm trying to follow this article (https://help.salesforce.com/articleView?id=creating_events_lex.htm&type=0) but I'm stuck at this step for Event Attendees:

• Admins have to add the Attendees field to the Event page layout or the quick actions layout for events. The Attendees field isn’t supported for Compact Layouts.

I don't have an "Attendees field." Is it an actual field like "Subject" or "Assigned to?" Or do they really mean a related list, which I also don't see available on my page layout. Do I need to enable something? I did the step just before that one:

• Admins have to set up Lightning Sync for users with the sync direction Sync Both Ways. Selecting Sync Both Ways limits some Salesforce Classic functionality. See Lightning Sync Considerations in Salesforce Help.