SSH To EC2 Instance Using Wsftp Pro

Hello I am new to EC2. I have created an instance and am trying to connect to the VM instance using WSFTP Pro https://www.ipswitch.com/ftp-client?cta=hphero.

From what I understand Amazon only allows SSH access using a Key pair and does not allow password access.

I have created a Key pair and downloaded the .pem file. The problem is WSFTP Pro requires the the key file extension to be .pub. I have tried renaming .pem to .pub but that did not work.

Please advise on what I am doing incorrectly. Thank you.