>> "that automatically opens somewhere during steps 1 through 7 with a "Activate..." button and does exactly same what your top menu button is doing in step 8."
Ok. You can do that. The example is just that: an example. You can change it however you'd like.
>> "Question: I can handle the code for the above scenario by launching a Windows Form, say, myActivationWinForm. But what I'm struggling with is where in steps 1 through 7 of your example should I open that myActivationWinForm. That is, where do I call myWinForm.ShowDialog()?"
It's up to you. Are you offering trials? If so, then stick with the current behavior (the customer will be able to use your app immediately, and when they're ready to buy they can).
But the flow is completely up to you. We made the best "general case". Making it work for your specific business needs are up to you.