Free version of Discovery Studio has not this ability to do docking, however, for docking of ligand-protein the first step is deep understanding of ligand and protein mechanism and recognize of protein active site based on their action to cause or make disease.
In practical step for docking after optimization of ligand that you do it by gaussian in the most case you don't need to optimize the active site of protein because this action will change the cavity shape of protein that will proceed by crystallization of protein in X-ray crystallography.