Hi Susmita,
You can create .f3d files from any programming or scripting language like Matlab or Python. It is basically a text file with a special extension. The details on how to set up file formats is in our documentation, typically located under C:/Program Files/Optiwave Software/OptiBPM 13/doc/OptiBPM_User_Reference.pdf. I believe what you are looking for is under page 744, Complex Data 3D File Format.
Cem