Hi,
Check with your BO Admin or Network team.They need to grant the file path access to the user which you are using to run the the BO applications.
After that at the time of scheduling the report you need to add the details in the "destinations" section->File System add the File directory path.
If you are looking to export the cross tab data in the CSV format then straight forward it is not possible.When you are going to schedule the report then in the CSV file you will get the data from Webi query not from the cross tab.
try to schedule your report with CSV format and select the "default enterprise" option in the Destination section and see how are you getting the data.
Amit