Boot Camp is the tool that Apple provides to repartition your hard drive and install Windows as a second OS provided you have Windows disks. To be honest, it probably isn't worth sacrificing all that space to Windows on a MacBook Air, they don't exactly have limitless space as it is.
Just run the game in OS X. It'll run pretty decently on your machine. The key advantage you have over the first generation of MacBook Airs is the 9400m nVidia GPU, it provides far more graphics performance than the Intel graphics in the first MBAs.