Create the exterior walkout area. You'll have to remove the earth from the exterior area where you intend to place the door so the ground outside the door is even with the floor of the interior basement. Use a shovel and wheelbarrow to remove the soil from this area. Be sure to dial 811 before you dig to arrange to have underground utilities marked. Some soil types need only to be dug out and landscaped to slope downward, toward the door, while others require the construction of retaining walls to hold back loose soil from the area. Consult a professional contractor to determine the best method for your soil.
Measure the intended door frame. Use a measuring tape to measure around the outside of the frame.
Remove the existing window and the frame. Your removal method will depend on the type of window you're removing.
Find the center of the top of the opening in the wall left by the window, and use it as a center point for door placement. Divide the width of the door frame by two to find the center of the door. Place the door frame flush to the wall, with the top center aligned with the center of the opening and the bottom flat against the floor (assuming the floor is level). Trace around the frame with chalk.
Place a chisel along the inner edge of the chalk line and hit it with a hammer to create a starter point for a masonry saw.
Cut along the drawn chalk line with a power masonry saw. Using a silicon blade, cut from the bottom up along the chalk line. If the wall is thicker than the blade is long, cut through as far as possible. Cut all the way around the chalk lines.
Chisel out the remaining areas of concrete, block or other masonry. If the first masonry saw cut did not go all the way through, make a second pass after chiseling out the center areas. Be careful of falling concrete during the cutting and chiseling.
Sand the inside of the cut opening. Use 60-grit sandpaper on an orbital sander to slightly smooth the opening.
Hold the frame in the opening and drill the holes for the screws. Select a doorframe that's the same depth as the wall. Have someone hold the frame in place while you push a drill with a masonry bit through the screw hole openings.
Screw the doorframe in place with concrete or anchor screws. Use a drill to tighten the screws through the frame and into the cut-out opening.