When loading up CAS you will be prompted with whether you wish to "create your sims story" or not.
Clicking on "No Thanks" brings you to the "old" CAS.
Clicking on "Okay" well brings you to the next screen. Choosing the Age of your sim.
After selecting the Age of where you want your sim to start out at, you will be prompted by a series of questions. Your answers will determine your sims:
All 3 traits
Note: You can skip any question you don't wish to answer.
Once you are all done your sim will appear as a male or female where you will be prompted to give them a name, change their gender, clothing and of course you can change their body/facial features as well.
You will also get a look at the story you have created for your sim.
Once you have decided on a world and picked out a place for your sim to call home, your starting out funds do change from the way it used to be.
Side note: Choosing to add more than one sim to the household you will get the option of creating their story as well with the exception of creating a child through using genetics, you will not be able to create their story.