Launch multi-core debug session with CMSIS-DAP/I-jet
Select the CM0 project and click the
Download and debug
button.
IAR builds all projects, programs all the separate images, and launches a multi-core debug session. IAR opens a separate IDE instance for each project specified in the session file. For dual-core MCUs, it should look like to this:

The left side of the screen shows the IAR IDE instance attached to the CM0+ core. The right side shows the CM4 (or CM7) core not started yet. Once the
Cy_SysEnableCM4()
function is executed on the CM0+ core, the CM4/CM7 will start executing its application.
You can step through the code by switching back and forth between the two IAR IDE instances.