If you're having difficulty attaching the hood to your poncho in this tutorial, here's another way to do it. Don't stitch the two layers of the hood together. First, separate the two body pieces of the poncho and then attach each layer of the hood to each layer of the body separately.
First, pin the hood to the slit in your poncho, right sides together like this:
Then sew the hood with a 1/4 inch seam allowance to the body.
This isn't the greatest picture, but when you get to the edge of the hood, fold over the edge of the hood about a 1/2 inch and sew. In this photo it's where the green pin is. This will help for when you will be sewing the two hoods together and the edges need to be folded under.
Repeat for the other layer. You now have 2 separate one-layer ponchos.
Then turn one poncho inside-out and place it inside the other. Turn down the edges of the hood and neckline and stitch all the way around.
Then stitch all the way around the back of the hood to secure the two body layers together around the back of the neck.