The AWS Server Manager is an application that interacts with AWS EC2 instances to turn them on/off and provide automatic cleanup as well as steam query info.
In ACP you can find all global application settings. AWS IAM credentials with programmatic access and EC2 permissions is required.
In ACP, under "Servers", you can configure different EC2 Instances, or "Servers". Depeding on the game, you need to supply the connection info, a name, as well as the steam query port. Upon saving you can configure which groups can start, stop or reboot a server.
Once configured, navigate to http://mysite/servers, here you will find different options to start/stop/reboot servers as well as how many players there are and so on from steam.
To save on EC2 credits or cost you can configure auto-shutdown. A backend task named "stopawsservers" runs every 5 minutes and scans all servers for steam info. Once the server has been empty by a configurable amount of minutes (under settings), it will automatically shut down the server.