Sew gathering stitches between the markings at the shoulders of both front sections and along the top of the back section. To do this, lengthen your stitch length on your machine as long as it will go and sew leaving long tails at either end of your stitches. (You can also loosen your needle thread tension if you like, but I don't find it necessary on my machine.) I almost always sew 3 rows of gathering stitches--one inside the seam allowance, one on the seam line, and one just a bit on the other side of the seam line, which will definitely have to be removed but which helps ensure even gathers.
Pull on your bobbin threads (all at the same time) to gather your fronts to fit the front part of the yoke, and the back to fit the back part of the yoke.
After gathering the pieces to fit, stitch the back to the back part of the yoke, and the fronts to the front shoulder sections of the yoke (being careful to make sure the center fronts are to the center). Finish the seam allowance with a serger or zig-zag stitch on your sewing machine, and press the seam allowances toward the yoke. Topstitch close the seam-line.
When you have both fronts and back section attached, it will look like this.
It isn't much, but that is all for today. Tomorrow, we'll handle the frills (which you can skip, by the way, if you prefer the shirt/dress without them) and attach the button bands and probably the sleeves.
If you have a serger and have never used it to make a rolled hem, get out your manual and read up on how to do it. If you don't have a serger, a sewing friend is going to put up a tutorial on her blog for how to do this on your sewing machine.
How is your shirt or dress coming along?!