Essentially, each ePWM block configures how a particular ePWM module on the F28379D board fires the ePWM signals.
Under Model Configuration Parameters -> Hardware Implementation -> Target hardware resources -> ePWM, you are able to specify which GPIO pin each PWM signal maps to.
I have attached an example of how this block would work, along with an image that provides a high-level overview of the configuration process.
Below is a link with more information about the capabilities of the ePWM block:
