Here goes. The first thing I did was get the window measurements and the pattern doesn't fit-- The largest pattern is too large and the smallest too small. Adjustments required. I would use the large sized pattern, but I would make adjustments to the size of the folds in the end. Oh yes, one other thing-- the pattern is designed so that the finished product is mounted to wood and mounted to the wall. We used tabs instead. The window was also long, so I moved the pattern down about 2 inches to add to the length.
As seen in the picture, the edges of the scarves were finished with a serger. As a result, I didn't really want to hem the bottom either. This fabric was thick with a plain back, so there was no need to line either.
I used some lace that I folded over the bottom edge.
Next I placed a measure tape next to the fabric- set to the required width of the finished topper. Using the pattern I calculated how much more I would have you use in the pleating to get the topper the correct size. As you see below, I put pins to mark the centre and the outside edges of the pleats-- about 3/4 inch more on each side.
I took the left pin and pulled the fabric in to the centre pin. Then did the same on the right. This was done for each section of the topper (as required by pattern). Then I pinned the pleat down to hold it in place.
Then I took a piece of lace and attached it over the top.