No vacuuming needed, make sure small hole in stat faces straight up to match the small hose entry in the front cover. The system pretty much bleeds itslef and quick then.
On Focus cars BOTH fans come on as one, they are both on low or both on high as needed.
The stat goes in with the smaller disc end toward back of car. Again, small hole in outer edge faces straight up. That hole may have a loose BB or little poppet trapped in it, I always take it out on mine. That stops it from getting stuck from corrosion later in life.