HERE - and here's a picture - the one in the package is a great deal and the one you'll want to get:
You just take that elastic thread and hand-wind it around your bobbin. Easy enough. Then pop it into your machine. Then sew - on the front side of your fabric (so the elastic thread is on the back side). I started 1/4 inch under the top edge of the shirt and sewed all the way around the the neckline- when you get all the way around, drop down 1/4 in and sew another line - I sewed a bunch (about 10), 1/4 inch apart. I sewed it in one continuous swirl so I didn't have to start and stop a bunch of time. Here's a couple of close up views..
Now, my favorite part of shirring - the magic! When you sew with elastic thread, it gathers a little bit but I've never that impressed. But then you shoot the shirred area with a blast of steam from your iron, and the elastic thread shrinks up on itself - like magic. So neat to see - here's a comparison (and there's a video of it in action on my Shirred Waist Skirt Tutorial)
That's it!! Really, this is SO doable!! A great project for a beginner sewer (the hardest part is the narrow hem in the armpit area) and especially for someone who wants to try out shirring.
I love this picture of my 1st grader - - it came out so great!!
So really, do try this - you can do it!