Show that for each $n> 0$, $Mat_n R$ is a ring. If $R$ has an identity, so does $Mat_n R$

Show that for each $n> 0$, $Mat_n R$ is a ring. If $R$ has an identity, so
does $Mat_n R$

How to show that for each $n> 0$, $Mat_n R$ is a ring. If $R$ has an
identity, so does $Mat_n R$ (namely the identity matrix $I_n$). Thanks