You created an EC2 instance and got private key (with PEM extension)from Amazon. Now, how you can login to your instance with PuTTY? For this, you need to convert the .PEM to .PPK format using Puttygen.
Click on the Load button:
Locate your PEM file that you want to convert:
Putty will convert the .PEM to .PPK format:
Select “Save Private Key” (passphrase is not required):
Launch Putty and enter the Instance IP address:
Navigate to Connection -> SSH -> Auth, Click “Browse” and select the .PPK file and Click “Open“:
When connection comes up enter username (default is ubuntu for Ubuntu and root for CentOS):
Hope this will help you!