Add link to excel spreadsheet from iSupplier Portal

I have been asked to assist developers and support staff in accessing a password protected excel spreadsheet from the iSupplier Portal. I put the excel file in $OA_HTML on the iSupplier server and can login through Juniper then in to E-Business and open the file from there. We have configured iSupplier using a reverse proxy.

My question: Is this the only place I can put a custom file to make it accessible by a URL from the iSupplier Portal or is there a custom location/url I should be using. I am the E-Business DBA and do not really know a lot about iSupplier, other than the underlying configuration of the external facing server.