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.
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.