How do you invoke the custom operation of function import at runtime

Hi,

     Could you please tell me how do you invoke the operation of a function import at runtime

Here is the code of my remote enable function module (ZF_EXPERIMENT)

FUNCTION ZF_EXPERIMENT.
*"----------------------------------------------------------------------
*"*"Local Interface:
*"  IMPORTING
*"     VALUE(A) TYPE  I
*"     VALUE(B) TYPE  I
*"     VALUE(X) TYPE  I
*"  EXPORTING
*"     VALUE(RES) TYPE  I
*"----------------------------------------------------------------------

RES = A + B + X.
RETURN.




ENDFUNCTION.

Here is the details of my metadata(i.e; the HTTP response )

this is my request URI ->  /sap/opu/odata/sap/ZMY_EXPERIMENT_SRV/$metadata

<?xml version="1.0" encoding="utf-8" ?>

Regards,

Prathik