Hi,
you can select the option "Response Surface Optimization in the Optimization workspace.
Afterwards, you can check the option "Use Result Pool"
It will ask you to select the pools which you want to utilize for the surrogate based optimization after starting the design engine. Please note that if you do not have sufficient samples in your result pool, it will do additional samples before starting the optimization. It will then perform the optimization on the surrogate in the background without calling CFD. After that, a new design will show up in CAESES, which is then evaluated using the CFD to check if it matches the prediction from the surrogate.