Hi Subhasini,
Go to Setup-->Document Setup-->Agreements-->Contract Data and Document Importer. There you can download the workbook template, there you would found the fields. If you dont see the option from your login then login through Enterprise and then download the template from the above path.
Coming to your second question, The system recognises the CD with the Unique name of MA and the name of the CD. It picks the CD whose name you have written in the DOC_DISPLAY_NAME.
Please visit below blog to get more information. Hope it helps.
Mass Update of Contract Document Fields via workbook in 7 Simple Steps
Let me know if you have any other queries.
Regards,
Kushagra A