How to make Fring work with VoIPover3G on iPhone

Does anyone know the procedure how to make Fring app work with VoIPover3G on iPhone.

Why: Cydia VoIPover3G lets you use iPhone's skype in Fringe and talk over 3G.

There are posts in the net explaining how to do that but I failed to get exact procedure. Will anyone help me on this one ?

VolPover3G is preconfigured to work with fring out of the box.