The key to wearing a tie neck blouse is to adjust the knot so it falls evenly with the fullest part of your bust line. This can give the illusion of a little more volume, if desired.
Essentially, you want to tie the neck of the blouse in a bow or knot, then adjust its position to be flattering. Experiment with different knot styles and placements to find what works best for your body type and the blouse itself.