How did Niels Bohr use Planck’s constant in his model of the hydrogen atom?

Niels Bohr utilized Planck’s constant ($h$) to resolve the stability issues of the Rutherford model and to explain the discrete spectral lines of the hydrogen atom.12

Bohr’s application of the constant included the following key steps:

• Quantization of Angular Momentum: Bohr postulated that electrons could only occupy specific stationary states where their angular momentum was restricted to whole-number multiples of $\hslash$ (where $\hslash =h/2\pi$).13
• Determining Atomic Size: Bohr recognized that classical constants alone could not define the size of an atom. By combining Planck’s constant with the mass and charge of the electron, he derived a measure of length consistent with the known size of atoms.2
• Explaining Spectral Emission: Bohr proposed that radiation is emitted or absorbed only when an electron transitions between these fixed orbits. The energy of the emitted photon corresponds to the difference in energy between the two states, governed by the relation $E=h\nu$, which allowed him to accurately calculate the Rydberg constant and the wavelengths of hydrogen's spectral series.12