To enable this option, go to Projects > Project Elements > Quote > Reports and check the box in the Instance Level Reports section for CrewDriver Export, then click UPDATE. You will need to reload any open Quotes to see the option in the Workbench Menu on the right-hand side.
For the export to populate correctly, you will need a valid Contact selected in Flex's "Venue / Site" field (typically the right-hand Address Block). You must also have at least one line item that has a Resource Type with an Availability Mode of "Labor or Staffing." By default, this would be Labor or Employee. If custom Resource Types have been created, or built-in Resource Types altered, you may need to update their settings.