You can find information in the controllers manual; i.e. KRC4, KRC4 compact, KRC5)
It depends on the safety you are using. If you have the robots connected to the PLC's just for standard IO, then you have to use X11 for safety. If you are using safety signals (CIP, ProfiSafe, FSoE), then X11 is not required, and you just need to place the small jumper on the CCU.
What are you trying to achieve?