I am not sure what you need help with - but here is how I do it. My Avatar had Y seams. I marked the three pieces VERY carefully at the 1/4 inch seam mark with a disappearing ink pen at the intersection point. I then "matched up that point on two of the pieces and pinned carefully away from the matched point. I sewed "from the outside edge" into the point -stopping about 1/8 to 1/4 inch short of the intersection (this allowed me some room to match up that point with the other side). I the did the other seam the exact same way. Match up the point first, pin carefully and sew. This time I went ahead and sewed up to the point. Then I either went back to sew the other seam if needed. Hope this helps.