Preliminary information on the problem can be found in every fluid dynamics textbook or on line. See for example wikipedia.
However, a key point to take into account when using the expression
$$
F_D=\frac{1}{2}C_D \rho_{air} A v^2
$$
is that $C_D$ is constant only over limited interal of velocity. For example, in an answer to a related  question you may see a plot of $C_D$ for a sphere, as a function of the Reynolds number, which is proportional to the flow velocity $v$.
So, while from the final velocity of a falling object it is possible to extract the value of $F_D$ and then of $C_D$, strictly speaking, that value of $C_D$ will be valid only for the corresponding Reynolds number. It is clear that at very low Reynolds numers ($Re \ll1$) a Stokes-like formula where drag force is proportional to $v$ should be more appropriate. In general, one has to measure $F_D$ at different velocities, in order to assess the value of $C_D$.