Take from the crate that's labelled Newts and Toads.
Place the label of the creature you removed on that box.
Place the other two labels on the other two boxes in either order and talk to Gus. If this is the wrong combination, swap the last 2 labels placed and talk to him again.
Take a newt from the newt crate.
Talk to Hetty. ( 2 ) …
Betty [ ]
Talk to Betty in north-western Port Sarim. ( 1 ) …