Add configuration instructions

README.md

@@ -17,7 +17,17 @@ def deps do
 end
 ```
 
+## Configuration
+
+Change the config for your mailer:
+
+    config :my_app, MyApp.Mailer,
+      adapter: Bamboo.SesAdapter
+
+To find more on AWS key configuration please follow [this link](https://github.com/ex-aws/ex_aws#aws-key-configuration)
+
+## Documentation
+
 Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
 and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
 be found at [https://hexdocs.pm/bamboo_ses](https://hexdocs.pm/bamboo_ses).
-