Making a hood to add to a coat involves a lot of detail work if you have to design the hood, but you can add a hood to a coat without designing the hood yourself. You can use the hood from an old sweatshirt jacket. Try the old sweatshirt jacket on before you begin to make sure the hood fits properly. Then you just have to get the hood off of the jacket and put it on the coat.
Push the seam ripper's tip under the first stitch you see in the topstitching along the bottom of the sweatshirt hood. Push the seam ripper forward without pushing into the fabric to cut the thread. Cut every third stitch in the topstitching, beside the seam holding the hood on the sweatshirt jacket. If your jacket does not have topstitching, the line of stitches running about 1/4 inch from the actual seam, go on to the next step.
Cut every third stitch in the seam holding the sweatshirt on the jacket using the seam ripper. Use your fingertips to pick out the thread ends left in the fabric.
Serge the bottom edge of the hood or use the zigzag sewing machine to finish the hood's raw edge.
Mark the hood's center back, in the serged or zigzagged stitching on the bottom edge, with a tailor's chalk dot.
Mark the inside, center back of the coat's collar with a tailor's chalk dot. Fold the coat in half with the coat's front lined up to find the center back. The folded edge of the collar will be the center back.
Stand up the coat's collar. Position the hood, so it stands up inside of the collar. Line up the tailor's chalk dots marking the center back of each piece.
Pin the hood to the inside of the coat's collar with the bottom of the hood 1/2 inch above the seam attaching the coat's collar. The 1/2 inch gap will allow you to sew without hitting the bulky layers of coat and collar fabric.
Set the sewing machine to make a medium-length straight stitch and sew the hood to the coat, right through the collar, using a 1/8 inch seam allowance. You will be sewing right up the centre of the finishing stitches you made earlier along the bottom edge of the hood. Remove the pins as you sew the hood and coat together.
Trim off the excess thread using the scissors and fold the collar down into its original folded position.
The stitching used to add the hood to the coat will be hidden by the collar when you fold the collar back down.