If you have an EC2 server it is great to install Webmin on it but it undesirable to expose it through the EC2 firewall.
An easier and more secure way to access it is using PuTTY to create a tunnel from a local port to a remote port. When you have done this you can access
https://localhost:10000 on your own computer and it will show you the Webmin on the remote computer.
It is very easy to do and there are instructions here. (replace the port shown with 10000 for Webmin).