Sew the neckline seam following the line you drew, being very careful to honour the 5/8" seam allowance. Clip at corners to but not through the stitching.
Trim your seam to 1/4" but leaving the tunic side slightly wider than the facing side. To do this, cut from the facing side and hold your scissors at an angle leaning toward the facing.
Press the seam allowance toward the facing side
From the right side of the garment , understitch on the facing side . ( Click on understitch for a review if you don't remember how)
At shoulder joint, if you have bulk, pound with a hammer gently to flatten out the seam.
Next time, I'll show you how to prepare for the sewing of the lines for chenilling.