Before you start
You need the Firestick on the same network you will watch on, your provider credentials, and about five minutes. No computer and no USB drive are involved.
If your stick is a first-generation model, plan to cap playback at 1080p afterwards — the hardware simply does not have the headroom for 4K.
Enable developer options
Open Settings → My Fire TV → Developer Options and turn on Apps from Unknown Sources. On newer Fire OS builds this toggle appears per-app the first time you install something.
If Developer Options is missing, go to Settings → My Fire TV → About and click the Fire TV Stick line seven times to reveal it.
Install through Downloader
Search the Fire TV home screen for Downloader, install it, and open it. Allow the storage permission it requests.
In the URL bar, type your provider's install address — for NixaTV that is nixatv.live/get — and press Go. When the download finishes, choose Install, then Open, then delete the installer file to reclaim space.
Sign in and tune playback
Enter the email and password from your welcome message. The channel lineup and guide sync in under a minute on first launch.
Then open the app's playback settings. On a 4K Max, leave quality on automatic. On anything older, set 1080p — it is the single change that eliminates most buffering complaints on older sticks.