The smart-mirror is configured using the Remote Configuration Tool. This requires you starting the mirror.
Open the terminal and type:
pm2 start smart-mirror (if you selected yes to use pm2 to manage starting during install)
If you're running the mirror for the first time (or for the first time since running upgrading to this version of the mirror) you'll see a QR Code with a URL under it. From a phone or another computer (on the same network as your Smart-Mirror) you can open a browser and manually enter the URL.
If you're not running the mirror for the first time and you've properly configured the Sound and Voice, say the keyword/hotword and then "Show Remote Link" to display the URL to reach the Remote Configuration Tool.
After going to the Home page click on Settings > Configure the Mirror.