How does one apply the knowledge of the direction of a molecular dipole moment?
Take a look at chemlibretexts. I'll just write an overview.



A dipole is a vector representing the charge distribution in a molecule. It's drawn from the positive-density charge side towards the negative. 

Some examples


Phase change 


How do we explain $\ce{CO2}$ fusion temperature is $-78\,^\circ$C while $\ce{SO2}$ is $-10\,^\circ$C? Because of its dipole magnitude. In the first one, there's no net dipole, but there is for the second one. 

The bigger molecular interactions the more they oppose to temperature-increasings. 


Solubility is higher for alcohols than lipids* in water. Again dipole-dipole interaction is stronger (energetically more favourable) than dipole-induced dipole interaction. 
CO$_2$ has no electric dipole in the symmetric vibration. According to quantum mechanics, if electric dipole does not change when it absorbes light of a specific energy, it will not be susceptible of a infrared measure. This particular vibrational mode will be (and it is) infrared inactive.