If you are not familiar with Linux, the minimal install that comes with the Hortonworks Sandbox can prove difficult. Fortunately, several bloggers have posted details on how to add a user interface to the Hortonworks Sandbox - and for that matter, any other CentOS minimal install that you may end up using.
Once you have made the changes, Hortonworks will display lots of logins, and none of them will seem to work - try admin with the default admin password. Does not work. Go to the bottom of the list, and log in as root. Then create a new user from the menu SYSTEM | ADMINISTRATION | USERS AND GROUPS. I also had to setup a network connection.
You can find the details here: