Let $C_n$, $C_m$ two cycles, show that $C_n * C_m$ is hamiltonian. Conclude saying that if $G$ and $H$ are hamiltonian then $G x H$ is hamiltonian

Question

Hi I need to prove this:

Let $C_n$, $C_m$ two cycles, show that $C_n * C_m$ is hamiltonian. Conclude saying that if $G$ and $H$ are hamiltonian then $G x H$ is hamiltonian

But i really don't know where to start, please help! thanks