Adding an entry limit to your event - this will limit the overall number of places available across the whole event.
E.g. there are 500 tickets across the event.

Click Settings
Click Events & fees
Click Edit
Add your entry limit
Click Save

Adding an entry limit to entry fee(s) - this will limit the number of places available per entry fee/ticket option.
E.g. if you have 40 adult tickets, 40 children tickets and 20 early bird tickets.

Click Settings
Click Events & fees
Click Edit on the entry fee
Click the Availability tab
Click Save

This will then appear on the entry fee.

Top tip! If you are adding entry limits to the overall event as well as the entry fees do make sure the totals add up.
Related articles
Adding wave times to your event.
Adding a waiting list to your event.