Muthu,
I think for the community to be able to help you, you'd have to be more specific on the difficulties you are encountering. For example, what FEFLOW version are you using (huge difference betwenn 5.x and 6.x), is the model 2D or 3D, are the aquifers different layers, ... In general, you can import and interpolate values from files to all kinds of selections of target nodes, but the procedure highly depends on the beforementioned circumstances.
Best regards,
Peter