Setup Assistant and Task Assistant refer to two separate tools that help you set up features in Google Analytics.
The Google Analytics Setup Assistant wizard in a Universal Analytics property helps you migrate from a Universal Analytics property to a Google Analytics property. It adds a Google Analytics property to your Analytics account that collects data alongside your Universal Analytics property. Learn more about adding a property to an existing Google Analytics account.
The Task Assistant tool in a Google Analytics property helps you finish setting up your Google Analytics property. Learn how to Configure your Google Analytics settings using Task Assistant.
Note: Setup Assistant has been replaced by the Task Assistant.