Learning Elixir--a fundamental question

I'm a new beginer with Elixir using IntelliJ.

Ok, I create my new simple Elixir module:

defmodule Geo do

   def rect(a,b) do

   end

end

Question: what are the next steps to call it? I should be able to Geo.rect(20,50) but how do I do that so it will execute?

Thanks. Also if you are a IntellIJ Elixir expert, I need a teacher; if interested contact me dandunne@sbcglobal.net