set up etcd cluster at AWS

I have no experience in cloud and etcd. Can anybody help me set up etcd clusters in AWS environment?

1. Set up 3 EC2 machines and install etcd and run them
2. I need to configure those 3 machines to communicate with each other. How do I do that in AWS? Do I have to configure with private IPs?
3. I will have one separate EC2 machine to run my application. And where can I get the address of those etcd clusters?

Please help me with this! Thanks!