How do you calculate the force of gravity between two objects?

$F = \frac{G {m}_{1} {m}_{2}}{r} ^ 2$, where:
• $F$ = gravitational force ($N$)
• $G$ = gravitational constant (~6.67*10^-11Nm^2kg^-2
• ${m}_{1}$ and ${m}_{2}$ = masses of objects 1 and 2 ($k g$)
• $r$ = the distance the centre of gravities of both objects ($m$)