First make a mark with chalk on both sides about 4 inches and a half, if you are more taller put one or two extra inches, with a rule make the line and cut it.

fold the front part of the the t-shirt, to make this align both sides of the seams to cut well the front part.

With the rest of the t-shirt cut two straps of 4 inches and a half open one seams, sew both straps together, iron about a half of inch to make the edge amd sew it.

make a ruffle with the strap you can sew it by hand or sew a long line and pick carefully.

Well i didn´t take pictures of the rest, so sorry!, when you made the ruffle pin it with the other part of the t-shirt i made a curve in the front part to sew the ruffle when the v neck beggins, or you can style it as you want, i sew the ruffle two times to give them more strength, sew the button and put a little strap piece to make the eyelet, if you have any questions just ask ^^