Running AWS CLI commands as ec2-user

I'm trying to use the AWS CLi for the first time, and I am doing it through putty by SSHing to the ec2 instance.

I want to run a command like "aws ec2 authorize-security-group-ingress [options]"

But I get the following error: "A client error (UnauthorizedOperation) occurred when calling the AuthorizeSecurityGroupIngress operation: You are not authorized to perform this operation."

I believe that this is related to IAM user credentials. I have found out where to create IAM users, however I still don't understand how this helps me to execute this command when I'm logged into the server as ec2-user or root, or run the command through CRON.

I have done a fair amount of reading regarding the access controls on AWS in their documentation, but I seem to be missing something.

How can I allow the command to be executed from within the AWS instance?