How to make Alexa turn off smartthings groups

Using Smartthings, Alexa, and Harmony. I just added a fan connected to an on and off switch inside my Xbox’s cabinet. Being a secondary Harmony hub, I had to say: Alexa tell harmony to turn on Xbox, After integrating Harmony with Smartthings, my activity showed up on Smartthings and now I can simply ask: Alexa turn on Xbox.
What I would like to do, is add the cabinet fan to run with the Xbox activity. I tried scenes, routines, but I have to turn them on, with no way to telling the same phrase to turn off. I have finally got webCore installed but never used and I’m not sure if that’s the way to go. Can someone help me achieve this? Thanks.

Doing some research I have found:

Still, I never had installed any pistons, not sure if I have to change the values “X,Y,Z” with my own routines names or if that’s the way it’s meant to be.

You can have switches, smart home devices, within the Harmony app to turn on/off with Harmony activities.

Just enable the appropriate SmartThings switches within the Harmony app settings. It’s also a good idea to turn on/off the “Harmony Activity” Switch that populates in SmartThings in the Harmony App. This will give instant updates for Harmony activities within the SmartThings apps.

You can put them in a “group” together in the Amazon Alexa App. E.g. If I say “ echo turn off the basement” all lights in my basement turn off.