Configure Site URL to send password recovery links

Our Metabase currently resides on an Amazon EC2 instant.

The Site URL of the Metabase instance is the default value: http://localhost:3000

So whenever a password recover email is sent, the link inside is useless. It looks something like this:

So how can I configure the Site URL of our Metabase instance so that it can actually be useful?

@daniel11 The Site URL can be configured via Admin > Settings > General.