SSTA is the system used to keep track of your time and paychecks. You'll enter your time into the system every week by Thursday at noon.
SSTA is managed by HR. They'll provide you with your login information, which you'll use to get into the system. Once you're able to log in, don't forget to update your time weekly: your supervisor will approve this time, and that's how you'll be paid. You can also access your paystubs and payroll information through SSTA at any time.