If you're the same age as Eren, Mikasa, Armin and etc., then follow scene 1:

Scene 1: You had decided to join the Training Corps. Now what awaits you in Training? What's your reason for joining?

If you're an adult and graduated already, then follow either scene 2 or scene 3:

Scene 2: You had decided to assist Instructor Shadis in training

Scene 3: You had chosen to observe the new trainees and see their potential. It is up to you whether you will help the trainees or not

Note: Amillia was injured in their last expedition, Erwin knowing her so well, he gave her a temporary make-up job that will do for a month. That's assisting  Instructor Shadis in training too. Rome asks your OC(if your OC is graduated) a favor to watch over Amillia since you and Rome are classmates in Training Corps along with Amillia.