Amazon Web Services is a very powerful way to run a virtualized server in the cloud, but there are some tips that will help you greatly when deploying a server for the first time. SSH access is one.
Changing the SSH port from 22 to 443 in the /etc/ssh/sshd_config file will help access when you are behind a firewall or a proxy. Then amend your Security Group to reflect the new changes.
The best SSH client for accessing your AWS instance is the Bitvise SSH client. This can import the SSH keys from your Linux instance directly without having to convert them as you do with Putty.
Many more Amazon AWS tips on this very useful web page: https://wblinks.com/notes/aws-tips-i-wish-id-known-before-i-started/.