Cut the straw to any length. Bend it to the size you want it to. Then you put a rubber band on it to make sure the ends wont come off. Then you just blow on it from the side and it will make a whistle sound.
Step 1: Done.
Step 2: Get a Box
step 1 find a big cardboard box thats only found in Africa
step 2 find rubber bands and tie them in the box
step 3 put your name in the box for good luck and you are done.