Okay, now we're going to adjust the gathers and sew the skirt to the tee shirt. This is a little bit tricky, but you can do it! Go slow, use as many pins as you need to, and don't feel bad if you need to do some ripping out!
First, lay your skirt on a table or ironing board. It should be inside out. Lay your tee shirt on top of the skirt. It should be right side out. Try to line up the side seam of the skirt with one of the sides of the shirt.
Now you are going to put the tee shirt INSIDE the skirt. The shoulders of the shirt should be aimed at the non-gathered edge of the skirt.
Pin the two pieces together at the side seam. Place another pin on the opposite side. Now you will need to adjust the gathers to fit the shirt. The skirt was gathered in two steps (in halves), so you can adjust the top part of the skirt to fit the top part of the shirt and then do the same with the bottom.
If your shirt is bigger than your skirt, GENTLY pull on the skirt gathers to smooth them out. This is why you left the enormous thread tails.
If your skirt is bigger than your shirt, find your thread tails, separate the two threads in the tail and GENTLY pull on one of them to make some more gathers. If one thread doesn't give, try the other.
Once the skirt opening is roughly the same size as the bottom of the shirt, adjust the gathers to make them even. You don't need to be obsessive about it, but try to make it as even as you can.
A bad distribution of gathers. See how there is a big straight part and a bunched part. That's bad.
A better distribution of gathers:
Put as many pins in as you need to feel comfortable! You can always adjust things as you go, too. I like to live dangerously, so I use minimal pins.
Now you are going to sew the skirt to the top. (Hooray!!!) Look at your tension and stitch length. Make sure they are not still set for gathering! Set your machine to sew a stretch stitch. Look in your manual to see how to do this. We will NOT switch to a stretch needle.
Sew around the edge of the skirt. Try to keep the gathering stitch on the skirt to the right of the needle. Adjust as you go and don't get too discouraged. Things that look like mistakes on the wrong side often are invisible on the right side. Go slow, try your best to keep the same seam allowance all the way around, and don't forget to secure the seam by sewing in reverse at the beginning and end.
Turn it all right side out and here is what you have:
Next up we will finish the dress with a hem!