Answer
See work below.
Work Step by Step
The angular velocity $\omega$ is the same for the rod and the small masses.
To find the angular momentum, find the moment of inertia and multiply by the angular velocity.
$$L=I \omega$$
$$L=(\frac{1}{12}M\mathcal{l}^2+2m(\frac{\mathcal{l}}{2})^2) \omega$$
