First of all you need a software to calculate the resistance (or better the power that is needed to propel your vessel). That could be products by ANSYS, Star-ccm+, FINE/Marine, Shipflow or similar.
Then you have to set up a parametric model, or, alternatively import a geometry and apply parametric variations in CAESES. To keep the same displacement, you can either adjust the draught of the vessel to meet the displacement, or you can apply transformation to the vessel that will adjust the displacement at the desired draught in a nested way.
Once you have defined the design variables that change the hull form, have connected to the CFD code of choice and calculate the performance, you can use those in a designEngine in CAESES to run automated optimization.
You will find some tutorials on each tasks mentioned in the tutorials shipped with CAESES, or in our YouTube channel.
Hope that helps to start with,