A doorknob handle assembly for retrofitting conventional rounded doorknobs, a kit for the doorknob handle's installation, and a method for using the kit to install the doorknob handle are described. The doorknob handle assembly has a doorknob handle in the form of a ring with an elongated lever extending from the outer circumference of the ring, the handle ring being threaded on its interior surface, and a locking ring having a threaded exterior surface and a slit defining a split ring. The locking ring is placed around the shaft of a conventional rounded doorknob, and the doorknob handle is placed over the face of the doorknob and threaded engaged to the locking ring in order to clamp the conventional doorknob between the doorknob handle and the locking ring. The kit includes a plurality of locking rings of various sizes and a locking ring wrench having a stub which seats in the slit defined in the locking ring for attaching the locking ring to the doorknob handle.