How do I "un-winterize" my sprinkler system?
I'm no plumber, but I did just install my own sprinkler system.  That looks like a reduced pressure assembly used for backflow prevention.  the little screwdriver valves at  bleeder.  You should only need to touch them if Water comes out.  With the main water under the house on, turn on the the big valve closest to the house  first, then the second valve closest to the sprinklers.  That should do it.

Google RP (watts makes them) and you should find plenty of info.  Poetically no exact matches on pictures, but ask the right parts in the right places