Measure the rough opening
Verify the opening is square, plumb, and level
Mark the window location on the wall
Install the king studs on both sides
Install the jack studs on both sides
Install the sill plate at the bottom of the window opening
Install the sill trimmer or cripple studs under the sill
Install the header above the opening
Install cripple studs above the header
Secure all framing members with proper nails or screws
Double-check the rough opening size against the window manufacturer’s specifications
Inspect the framing for alignment before installing the window