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1) Click on the field that you want to extract. When a field description has the word entity.
2) Click on the >> button to move the field into the selected fields.
NOTE
The << button will move the highlighted Selected Field back to the Available Fields column and the X will move back ALL the Selected Fields back to the Available Fields,
Criteria Selection
When you have defined the fields that you want to extract you can then define the criteria for the entities that you wish to extract. Refer to this article for more detail on specifying criteria.