Pretty good article with some quick tips. Also shows how to do a fresh install of win 10.
oh and @anon42851937 I think you were looking for this one.
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Get Cortana to start listening automatically just by saying, “Hey Cortana!”
You can enable this feature by clicking on the search field in the lower left-hand corner of the task bar and then select the Notebook icon that will pop up on the left-hand side. Then you should click Settings and turn on the option to have Cortana respond to you automatically just by saying, “Hey Cortana.” This will require a working microphone, of course.