All I had to do was use this: no pattern technique and went from there.
I cut an inch up from the band of the sleeve, at an angle, for the collar.
I situated the collar on the inside of the neck of the dress, pinned it, then flipped it upward
so I could sew it onto the dress (photo below)
I did this to both the front and back of the dress
It turned out really cute. Word of advise, DONT add 1/4 seam allowance, I did and regreted it.
I ended up having to take it in because it streches well and was waaay too baggy. Enjoy, have fun, mistakes
will always come along, let yourself make them, then let them slide off your back.