Once you've successfully launched an instance from the AWS Marketplace, you can connect to it from your EC2 Dashboard.
Select your instance and then click Connect. You can also select your instance, click the Actions drop-down list, and then Connect.
The Connect To Your Instance window displays with information about how to access your instance.
NOTE: You must already have the private key file (<your_pemkey_name>.pem file) and not be publicly viewable in order to use this instance.
Follow the instructions to access your instance, especially step 3 to change the permissions on your ".pem" file. By default, the file is located in the ".ssh" directory of your SSH client and set to 755 permission mode. It must be changed to 400, as shown, to limit who can view the file. If you do not change the permission on the file, you may see an SSH error warning "unprotected private key file" and permission is denied. Change it, and then connect to your instance.
If you are using an SSH client, copy and paste the SSH command shown in the Example area to your command line, and change the user ID to "ryftuser".
This example uses the Cygwin SSH client
For more connection information, see AWS Connection Documentation.