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.
When the environment comes up, customize the layout 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.