Select the instance that you want to attach an IAM role to.
Under Details, check the IAM role to confirm that the role is attached to the instance. If an role is attached, then be sure that changes to the role don't affect your applications or access to AWS services. Note: The instance permissions change based on the IAM role that's attached. Applications that run on the instance can be affected.
Choose Actions, Security, and then choose Modify IAM role. Note: Amazon EC2 uses an instance profile as a container for an IAM role. For more information, see Instance profiles.
For Choose IAM role, choose the instance profile that you want to attach.