FireHydrant has two main ways to break your application into smaller pieces. Environments are the larger of the two chunks, for example you might have a Staging environment or a US East environment.
To create and manage environments, click "Environments" on the left navigation. Then click "New" on the right side of the page. Or, just click this link.
On the New page, enter in the name of the environment, and (optionally) a description.