This support article applies to RSVPify 1.0 and 2.0.
In RSVPify 2.0
1. Open your event.
2. Click Setup.
3. In the left navigation, select Secondary Events.
4. In the event's menu, select Move Up or Move Down.
In RSVPify 1.0
Secondary Events are ordered on your form in the order in which they were created, but grouped by invite type (Ask All My Guests to RSVP for this Event to this event or I will Select Guests to Invite form My Guest List).
At this time, it's not possible to re-order events outside of these groupings.