I can't find the advanced color correction box on IMovie. Can someone please help me?

I have been constantly searching how to turn on my advanced tools on IMovie, but because the update is so new, I think they changed the format of everything. On every site, it says to go to your IMovie preferences and click and general and etc., but it doesn't even show more than one category! I am using widescreen borders that are green screen and there are white lines near the borders. I've been told to use the advanced color correction, which I can't seem to find. Please help me and thank you in advance!