If you need to change the capacity of your total seats available, you can do so by editing the capacity of your event.

To edit the capacity of your event,

1. Head to the Event Manager
2. Click on the name of your event 
3. When you find the correct performance, go to the 'Capacity' column.

4. Enter your increased capacity and then click the checkmark to save your changes.

NOTE: This functionality applies only for General Admission performances (events without a seating chart).  If your event has a seating chart, seats can be held by "blocking" seats.

Please see this discussion on how to block seats for a Reserved Seating Event:  How can I block out seats for an event or performance?