Before setting up the editor plugins, you need to install the global binaries needed by them.
reason-cli currently doesn't work on Windows, but it's not a hard requirement for using Reason; you still have great CLI build system diagnosis messages through BuckleScript, whose npm global package
bs-platform does work on Windows.
OPAM is the native package manager for OCaml. If you come from OCaml and don't have npm/yarn, you can optionally install this way, but be careful!
Make sure you're on OCaml
opam update opam install reason.1.13.6 opam install merlin.2.5.4
If your editor isn't behaving as expected with the above install, do the following:
which ocamlmerlin refmt ocamlmerlin-reason
It should spit out three paths that contain the word
It should say "The Merlin toolkit version 2.5.x, for Ocaml 4.02.3". Not OCaml 4.03, not 4.04, etc.