IGST / GST Refund for 100% EOU

Dear Sir,

For a 100% EOU Imports raw materials, and also make local purchase for their FG(finished goods production). After the export, how he can claim the refund on IGST paid on imports and also GST paid on local purchase ? 

Whether this will be granted as INPUT TAX CREDIT on their account ? or they will get the refund on their account? 

What all the documents do they need to submit to claim the refund ? 

Or they can claim this after filing GSTR1 , GSTR2 & GSTR3 ? 

Await your reply.

Rds

Sreekumar