Nikon D3300 - Manual (Page 211)

191 Playback and Deletion
2
Select pictures.
Use the multi selector to highlight
pictures and press
W (Q) to select or
deselect (to view the highlighted
picture full screen, press and hold the
X button). Selected pictures are
marked by a
& icon.
3
Press J.
Press J to complete the operation.
W (Q) button