It is unlikely that you will be able to create a report just using Disco Desktop. There is a File->Import SQL function in Desktop but the SQL will only be imported if there are all the necessary folders and joins in the EUL for the SQL. If you the folders and joins are not there then you will need Disco Administrator to change the EUL.
Generally, the easiest way to build a report in Discoverer is to create a custom folder using Disco Adminstrator and then build the worksheet based on this folder using Disco Desktop.
Thanks Rob... I have requested a user who have Disco Admin login to include this Custom folder and referring required BA. I'm not able to run the report in Disco Desktop..
Thanks for your help.