When adding a Big Rock task you will start by clicking the + button in the red box.
Next, you will give it a title, and add a due date. Then you can divide it into smaller subtasks.
When you go back, you will see the previous screen has been updated to include your new Big Rock Task.
Back on the Action Plan main page, you can now see that your new Individual Action plan is now listed.
As you complete your smaller task, your progress bar will fill with green.