Window AC install question

[M A V I C]

I'm confused by the bracket thing. If it goes across the window frame, then the unit wont sit flush in the frame and thus there will be big gaps on the sides across the bottom.

If it is just outside, there's nothing out there to screw into.



My window has no lip like that on the outside. No wood at all. There's just a small, maybe 1/2" lip that's part of the vinyl window.