Bravenet is not authorised to register .us domains.
Help4children.us has not been registered anywhere.
You can still use a .us name with Bravenet hosting.
1. Open a Bravenet account and register for hosting
2. Find a registrar that handles .us domains and register help4children.us through them
3. Follow the registrar's instructions for pointing the domain name to your web site
There are several different ways in which step 3 can be implemented so it would not help to give you instructions now if the registrar that you choose does it differently.