After creating the stories, all the key factors in a project have been touched, including lifecycle, resources and stories. Now what you have to do is to do WBS ( Work Breakdown Structure ) for each story and generate all the tasks required to finish this story.
Notes:  It is to finish all the tasks of the story, including but are not limited to design, development and test tasks.

1. Stories of a Project

On the page of Stories, you can do decompositions of a story.  You can also check the number of tasks decomposed. 

2. Task Decomposition

Now you can choose stories when creating taskd.  The link to related story can also be provided. 

3. Notes 

3.1 All the stories should be decomposed into tasks, including design, test, design, even machine procurement and test environment deployment.
3.2 The decomposition should be as small as possible. For example, a task can be finished within several man hours.
3.3 If a task need several people to finish, then it should be further decomposed.
3.4 You can batch assign tasks, if the type of tasks are routine work. For example, a routine work is to ask every team member to write a project summary. In this case, you can select the type as routine workd and then assign it to all team members.
3.5 The type of tasks should be set carefully, since it will affect automatic calculations in development stories. We will explain this later.
3.6 The tasks are best to be claimed voluntarily, since this will boost people’s enthusiasm to the utmost extent.