Velux windows and blinds

You need not only a Somfy account, you also need a Somfy gateway:

The app requires one of the Somfy gateways, TaHoma, Connexoon, Switch or Connectivity kit.

(Quote from the App Store)

I assume that this app is currently the only way to control your Velux devices with Homey.
If you have further questions about the app and your Velux devices, then I recommend you to use the related topic:

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