how does de broglie explain bohrs 2nd postulate

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Bohr's Second Postulate states that

allowed electronic motion are only in those orbits in which the angular momentum of an electron is an integral multiple of h/2π. 

or  in other words

that the angular momentum of an electron is quantized,

So, Angular momentum; p = m v r = n (h/2π)

Thus, we have in effect placed restrictions on the positions of electrons around the orbit of an atom by doing this.

now,

The DeBroglie hypothesis states that matter posses dual nature or it has both particle like and wave like tendencies. 

Now, the wavelength of the waves emitted is given as

λ = h/p = h/mv 

Now,

as a consequence of the DeBroglie hypothesis we can infer that electrons which were presumed to be matter are also wave-like in nature.Now, as electrons are wave-like we have constricted the positions that can be occupied by the electrons around the atom.

This is in congruence with the Bohr's Second Postulate of selective electrons positioning. So, we have used DeBroglie's Hypothesis to successfully explain Bohr's Second Postulate.