M-theory is a candidate for a theory of quantum gravity. Its fundamental objects are called M2-branes and M5-branes. The low-energy theory describing coincident M5-branes is poorly understood in many respects, with holography providing one of the most useful tools to further that understanding. It is known that the theory should possess solitonic solutions called "self-dual strings". I will review the holographic description of these strings, and show how calculation of entanglement entropy provides a way of calculating an important quantity characterising them: their central charge.