The Cortex Designer app is deployed at CDHB through InTune. You should be able to download it from the Comp Portal app on your device. The login is your usual DHB credentials. However, only Cortex form builders are able to log in to the application. To be set up as a Cortex form builder, please see your departmental Cortex rep who can request this.
If you are on a personal (BYOD) device, you will first need to register for an InTune licence - this is done on the ISG Self Service Portal under 'Move to InTune'. Through this process you should be provided with information on how to install Cortex on a personal device.