Hold the blind up to the top of the window casement and center it. Mark the location of each hole to be drilled through the screw holes in the headrail. If your blinds come with brackets, align the blind in the center of the casement, then mark around the each end of the blind. Follow the manufacturer's directions as to bracket placement. To ensure proper position, you may want to enlist the help of a friend to hold the blind in place while you mark it
Drill holes, keeping the drill perpendicular to the casement, through each marked position. Use the size of drill bit indicated on the installation instructions included with your new blinds.
Insert screw hooks or brackets into the prepared holes.
Hang the blind with the locking mechanism and cords facing toward the room. For blinds with hooks, MatchstickBlinds.com notes that you should tug on the cord to unlock the clamp and allow the blind to unroll completely. Blinds with brackets should be set in the brackets and secured in place with wing nuts or other supplied hardware.
Straighten the edges of the blind. Pull on the cords until both cords hang at the same length.
Install a cleat or tie-down device on the wall on the same side as the blind cord. The tie-down device is typically placed near the bottom of the window close to the sill.
Position the blind in the desired location above or even with the top of the window casement. Have your helper hold the blind in place while you stand back from the window to make sure the blind is even and situated at the right height.
Mark the placement on the wall, around the outer edges of the headrail or through the holes in the headrail, depending on the type of mounting to be installed. For bracket-hung blinds, follow the manufacturer's recommendations for proper placement.
Drill holes into the marked positions, using the recommended size drill bit. Hold the drill perpendicular to the wall to ensure that the screws will drive straight into the wall instead of at an angle.
Insert the screw hooks or hang the brackets, following the manufacturer's installation guidelines.
Hang the blind and tug on the cords to loosen the locking mechanism, allowing the blind to open completely. Straighten out the edges and adjust the cords to ensure that both pieces hang at the same level.
Install a cleat or tie-down mechanism near the bottom of the window on the side of the wall closest to the blind cords.