Next step is to flip one piece over the other piece, right sides together and pin in place. You only need two pins, one at the top and one at the bottom.. more pins will distort the seam line.
The directions say to sew with a scant 1/4 seam allowance. So, here are pictures of my sewing macine and how I usually do this.. Do you see the 1/4 inch mark on my machine? I align the edge of my piece with that mark.
Now, when sewing this seam, do not pull on the patches or try to manipulate them through the machine,,, just gently guide it without pressure.. Let the machine do the work, it will not stretch your seam....