Hope you are doing well
Please follow the steps given below:
1. First you have to convert the .pem file or the public key which you have downloaded from the Amazon AWS website into .ppk file or the private key using PuttyGEN software
2. Click on Conversion >> Import Key >> Select the .pem file
3. Now Click on Open >> Save Private Key [ Do not click on Generate Button]
4. You will get one .ppk file , this private key you have to select in the Putty
I hope this will resolve the issue.
Please let me know if you have any further issue regarding this.
Feel free to contact us in case you have any query.