Use the following tutorial to support the instructions in your Riva pattern booklet.
The instructions for this begin on page 28 of your instruction booklet.
Start by transferring the pattern notches onto the wrong side of back piece A. For the purpose of this tutorial, I will refer to each notch by its assigned number on the image below.
Begin by pinching the back fabric at notch four. Match notch 4 to notch 2. You will find the fabric folds at the point of notch 3.
Next, pinch the back fabric at notch one. Fold over your previous pleat, matching up to notch 3.
Peeled back to show notch 3 at the back:
Pin in place. Gently press the folds you have created in the directions indicated on the long vertical lines on the pattern.
Sew a 1/4" seam to hold your pleat in place.