what step?

You can set it up using the app. 

Could you please let us know who your internet service provider is?

Make sure the G20 is properly connected to the coaxial cable and then allow the gateway to boot up fully.

As ​@plemans suggested, you can perform the first step using the SURFboard Central app.

If needed, you can also contact your internet service provider to activate the gateway by providing them the HFC MAC ID.