You need to go to the Roccat website and download Roccat Talk and install that. If Roccat Talk is running, the two devices should be able to talk to each other. Next, open up the configuration on your ISKU keyboard and change the keymapping on the Easy Shift [Caps Lock] button to Roccat Talk > Easy Shift (all devices). The all devices setting means it will activate Easy Shift on your mouse as well. You can do a similar thing for your mouse so the mouse Easy Shift will activate your keyboard Easy shift if you want.