Nikon D3300 - Manual (Page 141)

121 P, S, A, and M Modes
A The Information Display
Flash compensation options can also be
accessed from the information display (
0 9).
A Optional Flash Units
Flash compensation is also available with optional flash units that
support the Nikon Creative Lighting System (CLS; see page 300). The
flash compensation selected with the optional flash unit is added to
the flash compensation selected with the camera.