I assume you were in the back area for the interview, go through the same process to get to the back.
Tell the them it's your first day.
They will process you.
Don't worry, you'll be fine.
Go to the guest service desk, or ask a team member at TSC. On my first day of cashier training, I told a Guest Service team member it was my first day of training. That person will find the GSA/GSTL (cashier manager) for you to get your training started.