This paper contains the user`s guide and reference manual of Miro software. This software is used for simulating propagation and amplification of laser beams in laser devices as Megajoules or NIF. The physical effects taken into account ar essentially: saturated amplification, absorption, Kerr effect, birefringence and aberrations. The models of propagation are either geometrical optics of parallel beams, or Fresnel diffraction. A graphic user interface as been included to allow interactive management of optical devices and results. A Unix environment with X-Window and Motif is required to run Miro. The user`s guide gives a short insight of the software. The reference manual details the physical models and the way they are implanted in Miro. (author) 33 refs.