Steady state forced response using modal superposition technique

Hi,

I have done the modal analysis of a simply supported plate. Now I need to find the forced response of the SS plate for a point forcing. The transverse (perpendicular to the plate) point load is harmonic (say F cos(wt) ,where F is magnitude and w is frequency in rad/s). I need a steady state response. i.e displacement field at a given time instant. 

Is it possible to use the mode set from the modal analysis and get the solution as a modal superposition of those modeshapes ? If yes please help me out with the steps roughly.

regards,

Vachan