When you stand up an instance on AWS you are presented with a PEM file as the key for SSH into your newly stood up instance. This doesn’t directly work in Putty when you want to connect, but converting it into a format that works with Putty is very easy. If you only have Putty, you will need to also get PuTTYgen. I personally just got the whole installer, it is available here.

1. Once obtained and installed, open up PuTTYgen.
   
2. Click “Load”, and change the file types to “All Files (.)” and open your PEM file.
   
3. It will notify you that it successfully imported the foreign key, click “OK”.
   
4. Under “Parameters”, ensure “RSA” is selected, and the “Number of bits in a generated key:” says 2048.
   
5. Then click “Save Private Key”. It will prompt you that you do not have a passphrase, click “Yes”.
6. Select the location, name it, and save it. At this point you now have a Putty compatible key.
   
7. Connecting with Putty is the next step, open Putty.
8. Type in the IP or hostname of the instance you want to connect to.
   
9. On the left, under Connection and SSH, click on “Auth”. Under “Private key file for authentication” click “Browse” and locate the PPK key file.
   
10. At this point you should be able to connect to your instance. If you get an error saying your key is refused, you likely selected the wrong key.