Parbes

Hello, i'm in desperate need of help, I just bought KSP on Steam for my mac and it is VERY VERY laggy, i've closed every thing other than Steam and KSP and it still lags, can someone please tell me how i can remove the lag so I can play properly? I'm also quiet new to this gaming steam thing as i've only every bought and played Football Manger which works fine on my mac. Processor: 2.66 GHz Intel Core 2 Duo Memory: 4 GB 1067 MHz DDR3 Graphics: NVIDIA GeForce 9400 256 MB Thanks in advance.