These will have to be known to you or provided to you by someone on your team. AWS does support setting the root password which you can change by modifying the database.
Your security settings may prevent access from anyone on the internet. AWS uses security groups to do much of its network level security. Click on the security groups to view the inbound rules that will allow your client machine to connect to the database.
Find the IP address of your machine. Oftentimes you can just search for this online.