Press ALT+CTRL+T to access crosh shell screen – it will open new tab in yourChromebook. Now you have to enter these commands per line ssh,host,key and connect as show bellow – my user name, IP of EC2, my AWS key and connect to execute the connection.
crosh> crosh>ssh crosh>user root crosh>host 100.100.100.100 crosh>key MyAWSKey.pem crosh>connect
If all the credentials, IP, Key are correct you should be able to connect over SSH to your Amazon EC2 instance from Chromebook crosh shell. Now you can do all the fun things as usual and administer your server over ssh on Amazon EC2.