Examine the window, and decide what kind of rod you will need to use. If there is at least 4 inches or enough space for the mounting hardware above or to the side of the window, choose any type of decorative rod you like. If there is not enough space, choose a ceiling mount rod or a wall mount rod with brackets that go all the way around the rod so the rod will remain secured to the mounts.
Measure the distance from the floor to the ceiling and the width of the window you wish to cover. If there are moldings, you can choose to cover them completely or mount the hardware to the outer edge or center of the vertical trim. Purchase curtain panels long and wide enough to cover the dimensions.
Hold the brackets up to the wall or ceiling, and mark each screw hole. Check for level or that the brackets are the same distance from the corner of the wall and ceiling; adjust as necessary.
Drill a pilot hole one size in diameter smaller than the mounting screws through each screw hole mark not backed by molding or a framing stud. Hammer a drywall anchor the same size as the mounting screws into each hole.
Fit an electric drill with a Philips screwdriver bit, and mount the brackets to the molding or drywall anchors.
Thread the rods through the curtain rod pockets, and secure the rods to the mounting brackets.