Hi Venkat,
Thru some ABAP program you need move your flat file from source folder/network drive into Application server(AL11), then only you can trigger your process chains.
There are function modules, by using those also you can achieve this.
FM -
ARCHIVFILE_CLIENT_TO_SERVER
RCHIVFILE_SERVER_TO_CLIENT
http://scn.sap.com/docs/DOC-32322
Thanks