Link Zoho workdrive with Subform file upload

Link Zoho workdrive with Subform file upload

Hello Zoho Users,
i'm trying to link a file to a subform file upload field using ZOHO crm API, 
i looked all over in the documentations but there is not indication how to do that!
to recap:
i have a file object ( link / id etc ... for zoho workdrive ) andi want to add it to a module subform in File Upload Field!
thanks.