@Penabby Stay stitching is a line of stitching that is done literally just next to the seam line in the seam allowance (and I am talking a whisker or 2 away) and is used to stop the fabric stretching in places such as v-necklines, where the v is on the bias, and on curved edges. Sew this very carefully, taking care not to stretch the fabric, sewing each side in the same direction (ie dont do it in one hit going down one side and up the other, and actually, that is a good point for all sewing, always sew in the same in the direction - I always do down - so that if the fabric does move at all it moves in the same direction) and then continue making up.
As regards the pleat placement, in the absence of instructions, I would pin on the facings and then pleat/fold the main fabric to fit accordingly.
And never be afraid to ask, no matter how silly you think it is, we will always help and we will always be kind. You'll never learn if you don't ask