The Inbox is meant as temporary storage. Whenever something comes to your mind, just offload it to the Inbox. You should however review the Inbox regularly and move the Tasks to specific projects. But first go to the Inbox by selecting it from the Organize Library (1) or by pressing CMD-1. If you cannot see the library on the left side select View > Show Library from the menu to display the Organize Library again.
Now click "Add Task" (2) to create your first Task with Organize.
When you create a new task it is automatically activated and the task title is preselected (1). To change the task title just start typing. As the predefined title is selected, it will be overwritten as soon as you start typing your new title. Type "My first Task" as task title and press Return on your keyboard to save the task.
Organize:Pro has a setting to automatically activate the in-line editor, whereas Organize:Me automatically activates the Task Inspector.
After pressing Return the task is saved and the entry is displayed in compact mode again.
In-line editor and Task Inspector are available with both editions of Organize and you can change your preferred editor in Preferences > Display > Default Editor.
You can easily make any task a subtask of another by drag and drop.
As an alternative you can select a task, then press "Add Task". This creates a new task as a subtask of the current selection.