Setup Assistant launches when you start up a new mac or boot a used mac that doesn't have a user profile. As part of the setup process, it asks if you'd like to migrate data and gives you the option to choose the source of the data and the kinds of data you want to migrate such as Apps-Documents-System Settings-etc. This part of the Setup Assistant employs the app Migration Assistant located in your Utilities folder. Just choose them all and allow it to proceed. Migration Assistant can also be run separately from the Setup Assistant.