If you are running the workshop on your own, the Cloud9 workspace should be built by an IAM user with Administrator privileges, not the root account user. Please ensure you are logged in as an IAM user, not the root account user.
If you are at an AWS hosted event, follow the instructions on the region that should be used to launch resources
Go to Cloud9 Console
Select Create environment
Name it emrworkshop, and take all other defaults
When it comes up, customize the environment by closing the welcome tab and lower work area, and opening a new terminal tab in the main work area:
Your workspace should now look like this:
If you like this theme, you can choose it yourself by selecting View / Themes / Solarized / Solarized Dark in the Cloud9 workspace menu.