The guest seating and management tool Attendee Manager may not be currently enabled in your Event.
If you only see the blue Venue Mapper tab in the upper left...
...open the Event Information window by clicking either the Name of the Event or Event Settings in the upper-right.
In Event Information, check the box next to Guest List Enabled and then select Done.
The pink Attendee Manager tab will now be visible in the upper-left of the Event! Select that Pink tab to access Attendee Manager.
If you cannot Enable the Guest List from the Event Information window, Attendee Manager may not be included in your current Social Tables package. Please contact firstname.lastname@example.org for further assistance.