i need to replace the window rear o/s how do i begin?

In the door handle/ window winder arm " if not electric windows" there should be some small plastic caps/plugs that can be removed with a small screwdriver to reveal screws / clips etc. undo these and eventually the door card will come off. You may have to lift the card from the botom pushing it upwards to release. Generic answer, hopefully this will help.

Marl
November 2012