On first launch, System → Tools lists FFmpeg (required), fre:ac, MakeMKV and slskd with install steps for
your platform. Close it with Skip for now / Continue; it stays available in the System menu.
Open Settings → Connections, enable Radarr and/or Sonarr, paste the URL and API key, click Test, save.
Add Prowlarr for raw indexer search, Lidarr and slskd for music.
Check System → Status — it lists the ffmpeg version and which encoders are actually available, and flags
anything missing (ffmpeg, MakeMKV, fre:ac, a drive that disappeared, a path an *arr app reports that Rexarr
cannot see).
Add path mappings if Rexarr sees your media under different paths than Radarr / Sonarr do (typical with
Docker or a remote *arr app): Settings → Path mappings, remote path → local path, per app.
Pick default profiles per media type (movie / TV / anime / music) under Settings → Encoding → Defaults, or
create your own under Profiles.
Search for a title. If it is not in Radarr / Sonarr yet, Rexarr can add it. Choose a profile, click Grab
on a remux. The job appears in Activity as Waiting for import and starts encoding once the *arr app has
imported the download.
Or go to Movies / Series, filter to Remux only and transcode files you already have.
Turn on Auto transcode so every new remux is encoded without you asking, and add
a webhook in Radarr / Sonarr so it starts seconds after each import.
Turn on AniDB if you keep anime — it fixes anime movie detection, romaji titles and disc
identification.
If you rip discs, read Disc ripping: the rip directory has to be reachable by
Radarr / Sonarr, and Check import access tells you before the first disc whether it is.
Set authentication (Settings → General → Security) if Rexarr is reachable from outside your network, and take
a first backup (System → Backup).