Well, i don't want to keep you guys reading forever, so I will go on with the show.
Step 1: Step One: What You Will Need
3. A marker ( if you want)
Step 2: Step 2
Step 3: Finished!!!!
This is how it should look by now.( See picture) The top part that you cut off should be able to slide up and down the rest of the bottle, but should also fit snug. The way you use it is to slide the top that you cut off, up and down the other half of the bottle. Make sure that the screw cap is not on the bottle. If you want you can add ice and it will make the air that gets pumped out, a lot cooler. Another thing that you can do, I didn't do it, but you can put a piece of 1/2 inch PVC pipe in the bottle neck and it will be easier to pump.
Step 5: How to use it
It is very easy to use, but if you don't understand flip through the attached pictures.