Add directions for using with MongoDB Ecto

README.md

@@ -158,6 +158,22 @@ Mongo.find(:mongo, "collection", %{}, limit: 20)
 
 More pool options in [here](https://hexdocs.pm/db_connection/2.0.6/DBConnection.html#start_link/2-options).
 
+
+### Using with MongoDB Ecto
+
+If you're using Mongo with the MongoDB Ecto library, where you have it defined in your config/runtime.exs like this: 
+
+```elixir
+config :my_app, MyApp.Repo,
+  url: "mongo connection url"
+```
+
+You'll want to do reference mongo like this: 
+
+```elixir
+Mongo.find(MyApp.Repo.pool(), collection, %{_id: %{"$in" =>"some_ids"}})
+```
+
 ### Replica Sets
 
 To connect to a MongoDB cluster that is using replica sets, it is recommended to