Check we have it installed with:
$ elixir --version
Erlang/OTP 23 [erts-11.0.3] [source] [64-bit] [smp:12:12] [ds:12:12:10] [async-threads:1] [hipe] [dtrace]
Elixir 1.10.4 (compiled with Erlang/OTP 23)# jump in to this directory
cd elixir
# install the dependencies
mix deps.get
# run the tests
mix test
# watch the tests
mix test.watch
# run the repl
iex -S mix