How to optimize on graphics card? Another version of Cuda is already installed, do I still need to install the specified Cuda version? If yes, how do I do it?

To use the interface you don't need to install anything but start the solver als follows:

CudaPCGSolverDouble_cuda_10-1_gcc_4-8-5 1234

In the config of the optimization the IP and the port must be specified ("localhost" and "1234").

Yes you need to use the AMendate CudaPCGSolver so that the TCP interface is used.