Verify downloads against SHA256SUMS before installing. Upgrading from Readarr: see docs/migrating-from-readarr.md.
Windows users have two options: Librarr.<version>.win-x64-installer.exe installs to %ProgramData%\Librarr and can register the Windows service for you, or the win-x64 / win-x86 zips are a portable build — unzip and run Readarr.exe (tray) or Readarr.Console.exe.
The Windows binaries are not code-signed, so SmartScreen will warn on first run — choose "More info" then "Run anyway", or verify the checksum above instead.