1. Login to your bravenet account
2. Under the Web Hosting table area is a button that says Add website. Click it
3. Click on bravehost button
4. Click the button under the FREE table area where it says sign up now
5. Click build a new website
6. Then click on use a SUBDOMAIN
Enter an easy enough subdomain in that white box and hit submit and your SUBDOMAIN should be available.
Some people tend to think they need a DOMAIN but you want a FREE SUBDOMAIN