After logging into AWS, I chose the the public ami-47c5252e (Oracle published AMI) and started the instance. Instance started successfully.
Public DNS: ec2-184-72-84-130.compute-1.amazonaws.com
Save and generate the public key using puttygen
Download and save the *.ppm file from AWS instance. Use puttygen.exe to load and create private key. Puttygen does not recognize the .ppm extension, so change the filetype and then open .ppm file and save it as .ppk extension.
Using putty.exe initiated the telnet session to my instance.
Logged in as ROOT and installed the Oracle version 11g using preconfigured DBCA.
To enable password based login to the instance, edit the sshd_config file and restart ssh deamon
$ vi sshd_config
$ /etc/init.d/sshd restart
Stopping sshd: [ OK ]
Starting sshd: [ OK ]