Add Rule to EC2 Security Group for Inbound CouchDB Traffic
Your EC2 instance will need to have a new rule added to its security group allowing inbound traffic on CouchDB's configured port. It will most likely be a "Custom TCP rule" allowing all inbound traffic access to port 5984. The AWS docs I've linked to explain how to do this. After adding the rule, reboot your EC2 instance.
Download Dependencies then Configure & Install CouchDB
Test and Secure CouchDB Install
You can test your CouchDB installation by visiting the Futon util in your browser at http://x.x.x.x:5984/_utils. Using Futon you should immediately add at least one admin user to crash the "Admin Party". Also, you should prevent non-admin user's from accessing the _users database to better secure admin user names from prying eyes. Here are some good articles on how to secure CouchDB: