Sitl simulation

I am not new to multirotor operation but all my experience has been with Naza. I am a real Newbie to Arducopter and Pixhawk. My question is about Sitl Simulation. When I go to simulation in Mission Planner, I choose the Quad and it tells me that it is downloading the Sitl program. Everything looks OK except I don’t seem to know how to actually start the simulation. I saw that HIL could be used for simulation with FlightGear or X Plane but when I follow the directions I have no option to download the Copter in Hil format through MP 1.3.44. I must plead ignorance with this system and request some basic guidance here.

  1. Is the SITL portion of MP a stand alone program or are peripherals required? If not how do I start the simulation.
  2. Is HIL not an option in 1.3.44? I read in one comment that there is a Sitl transition underway.
    Any guidance would be appreciated.