[Lil Sis]

without seeing a pictures I am going to try to help-- or maybe just confuse you more lol

I open the collar and attach the collar..one side--right sides together to the dress. I then turn the collar correctly and attached the turned under edge by sewing by hand. You could attached that edge by top stitching

OR

attached collar by surger...there will be a narrow surger seam on the inside of the garment.

Remember the side you sew on will have the most "ease"

of course if the dress is lined there could be other ways.