Install a curtain rod for the sheers first. This rod doesn't have to be decorative, as you won't be able to see it behind the thermal drapes. A sheer curtain rod that is very easy to install is a magnetic rod. Place two self-adhesive magnetic brackets just above the window, one above each side of the window.
Insert the curtain rod through the sheer and place each end of the rod inside one of the magnetic brackets.
Install a decorative curtain rod for the thermal drapes. You will need a medium- to large-sized rod to support the weight of these types of curtains. Place one of the brackets for the rod about an inch higher than the bracket for the sheer curtain. Slide the decorative bracket about a half inch to the side, as well, so that the thermal drape will sit high and extend wider than the sheer. Mark and drill holes in the bracket. Do this for the other side, as well. Attach the brackets by placing them against the wall and screwing the screws into the holes that you drilled.
Insert the decorative rod through the thermal drapes and place the rod into its brackets.
Mark where you want the tiebacks to go and drill holes for any necessary screws for this hardware. Screw the tiebacks into the wall on either side of the window.
Pull the thermal drapes to either side and secure them with the tiebacks if you want to allow more light to pass through the sheer during the day. For optimal energy-saving functioning, release the thermal drapes from the tiebacks and allow the drapes to cover the entire window.