representation of extraspecial group

Question

Let $H=\langle x,y\rangle$ be a non abelian group of order $p^3$ which has exponent equal to $p$. Also let $G$ be an extraspecial group of order $p^{2r+1}$ exponent $p$. We know that $G$ is isomorphic with central product of $r$ copy of $H$. I want to know if we can say any thing more about presentation of $G$? for example if $r=2$, then how we can say about representation of $G$? is it generated by its elements? and what we know about the commutator of its generated elements?