Installing pre-made windows and doors

Hi. I just started building my teardrop (will post pictures soon) and wondering how I will fix my pre-made windows and doors. I purchased these doors and windows http://teardroptrailerparts.com/Windows___Doors.html
My side walls are 3/4 birch (from home depot) and will have 1/2 insulation on the inside covered with 5mm ply. My guess is that the screws they supplied are very short for my application. Also, I do I just then screw the inside frame to the door and the compression fit will hold the door in place?
thanks
My side walls are 3/4 birch (from home depot) and will have 1/2 insulation on the inside covered with 5mm ply. My guess is that the screws they supplied are very short for my application. Also, I do I just then screw the inside frame to the door and the compression fit will hold the door in place?
thanks