I don't know if it was right or not, but we never added flashing on a vinyl or metal clad window like that one in the picture. I don't ever remember actually having instructions with the windows, but I'm sure they were there on the job site somewhere. Then again, not a lot of rain here, either.

We would caulk the exterior trim boards around the perimeter of the window, and the top of the upper trim board.

__________________
Jim Robinson
New Mexico, USA