Add a few lines about connecting to the cromwell server through session manager

Author: tthyer

docs/orchestration/cromwell/cromwell-overview.md

@@ -210,6 +210,8 @@ This value can also be supplied as a Java command line variable.
 
 ### Accessing the Cromwell server
 
+The Cromwell EC2 instance may be accessed using the [AWS Session Manager](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/session-manager.html). Please note that by default this will log you in as user `ec2-user` in the directory `/usr/bin`. You may prefer to become the ec2-user with the command `sudo su - ec2-user` which will switch you to that user's home directory.
+
 ### Stop / Start / Restart the Cromwell service
 
 The CloudFormation template above installs Cromwell as a service under the control of `supervisorctl`. If you need to make changes to the `cromwell.conf` file you will want to restart the service so that configuration changes are included.