Let's see if i manage to do this right =)
Well... you'll have to cut the long piece (2) twice, one in black, and one in white, and sew them wrong sides together.
The length of that piece woud be the length of your torso + half round your neck. The thick middle would go around your neck and the wide parts would to the front of the top. You've to cross them in the front an inch or two so your boobs won't come out =P. To make it two-colour you'll have to twist it once in the neck area, and sew one black side to one white side in the front.
for the waist (1), you'll have to measure your waist and then think how wide you'll like it to be, and draw a piece two times wide, and then fold, so when you sew it to the twisted piece, you'll be able to put it inside and have a good finish =)
and then, sew the elastic (3) CUTE ribbon to the back, so it stays all together...
hope that'll do... i mean, this's not my mother language so i'm sorry for writing so awfully *blushes*