Dressing windows is much easier than most people might think. The key to success is to frame the window and not cover any of the glass. Think of the fabric as a frame and the glass as a piece of artwork.
Sidepanels should be hung 12″-18″ outside of a window so that the fabric drapes along the side window molding and to the ceiling on standard room heights. Valances should be hung to the ceiling with the bottom just covering the top molding of a window.
This effect of “framing” a window allows for full views and full sunlight while also making the window appear larger. When windows are dressed properly, the effect is an expanded space and a room that feels larger.