For Blood Knot the rights are administered by
William Morris Agency
151 El Camino Dr.
Beverly Hills
CA 90212
USA
It is worth mentioning if your performance is professional, semi-pro or amateur, as well as where it will be staged, the size of the theatre (seats) and whether admission is paid of free.
Also your background including, if you have them, reviews and why you want to stage Fugard.
Let us know how it goes.