If your event doesn't have labels associated with it, you can track attendance in a couple different ways.
Add from the Check-Ins Tab
You can add people to locations from the Check-Ins tab in an event.
Create a form and use automations to check people into an event.
Check In with Church Center App
Allow people to check themselves in directly from the Church Center app.
If you don't need names of people checking in, store the number of people who attended the event in Headcounts.