Summary: in the opening Using a level I shimed the window until it was level on the bottom and side of the frame then screwed the window into the old window frame with the long screws provided Once the window was shimed and screwed I rechecked the window with a level and measured from corner to corner to make sure the window was square Then I used the Great Stuff window and door
Image Dimensions: 468 x 484
Image originally found here.