An installation as simple as simple as hiring carpenter to the local hall and are available or order the homes construction ie masonry or order the local hall and either buy.

Opening of windows, Kind of windows, how to install window, local code of high and other opening .
Code : No higher than 44″ from floor
Code : Min 32″ from door opening
install must be leveled (horizontal and vertically)
Install must be easily to fit frame (No pressure , no loos )
around window frame must fill by fume or other insulator
insulation paper must be install before installation frame and minimum 4″ cover around of wood frame.