On Your Smart TV or Streaming Device: Go to your device’s app store and search for Plex. Once the app is downloaded, it will prompt you to use a phone or computer to go to plex.tv/link, sign in on that device (see steps below) and then enter the code you see displayed on your TV into your other device to link them. Once done, your TV device should now be signed into your Plex account. You may see a prompt to confirm your home screen layout - just make sure you at least have the Nevflix Movies and Shows libraries selected.
On Your Computer: Simply go to plex.nevflix.us in a web browser. Hit Sign In, Continue with Email, and sign in.
On Your Phone or Tablet: Download the app from your respective app store and sign in.