The default username and password differs between Linux distributions. In the table below you'll find the default username and password for the image you used.
If you want to access the console, you will need to configure the password for the default user during the creation of your instance. Please read the article Configuring a password for the default user for more information.
Usernames and passwords
When the table says "SSH key", you don't need a password for your instance. At the creation of your instance you have specified an SSH key that should be used for the instance. With this key you'll be authenticated when connecting to the instance from a remote computer.
For more information about creating and using SSH keys you can read this article: SSH key pairs