Hi - this is how you would put pockets into the side seam of a garment.
First you need to sew the pocket piece to the jacket body piece right sides together using a 3/8" seam (assuming you are using the standard 5/8" seam allowance).
Press the seam toward the pocket.
Then sew the jacket side seam RST down to the pocket, around the pocket, and down the remainder of the seam.
Turn right side out and you have a pocket in the side seam!
Hope this helps!