Updates to readme

README.md

@@ -4,6 +4,8 @@ This plugin permits encrypting storage contents in Rundeck using an Amazon Key M
 Key. This enables encryption and decryption of secrets in Rundeck without the actual secret key
 installed on the Rundeck server via the KMS API.
 
+# Usage
+
 ## Requirements
 
 This plugin requires Rundeck 3.3.9 or newer, as that's the version of the Rundeck APIs we're
@@ -19,6 +21,17 @@ If I get interest in a version of the JAR that uses a _shared_ AWS SDK, I'm happ
 That would work better for folks who already package the AWS SDK in Rundeck's classpath in its
 entirety.
 
+## Authentication
+
+If you're running Rundeck within AWS, you canuse instance roles to assign the
+proper permissions for Rundeck to access KMS for the use of this plugin.
+
+I still need to add code to handle passing these values in from configuration.
+
+For testing purposes, you can also set AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY
+as with any other AWS library, though there are likely reasons this ins't good
+in production.
+
 # About the Author
 
 I'm Matt Farmer, a Staff Engineer at [Greenlight Financial Technology][gl] in