A good way to install a window in a metal frame construction is to use some light gauge angle and screw it onto the sides of the window leaving a 10mm space for plaster. A flat head, self tapping screw is used to fix the window to the frame. Watch this video tutorial for a demonstration on how to install a window in a metal frame.
The angle will also create a good window flashing.
Want to master Microsoft Excel and take your work-from-home job prospects to the next level? Jump-start your career with our Premium A-to-Z Microsoft Excel Training Bundle from the new Gadget Hacks Shop and get lifetime access to more than 40 hours of Basic to Advanced instruction on functions, formula, tools, and more.