Creating EC2 Access w/ PEM Keys For Other Users

I'm indeed new to AWS and EC2, but I'm going to rip my hair out on what should be a simple process. I have created several server instances. I can ssh into them with my pem key just fine. However, when I create a new user through IAM, they can create a keypair that won't allow them to access any of the EC2 instances through SSH. I can give them full access to EC2, and they still can't login to ssh. What's the deal here? Do I actually need to login to each server and create and delete users? What is the most simple way to create an additional user and then revoke/suspend access? I'm going to rip my hair out.