Then just follow the instructions on the paper to craft it. You have to combine two items to get a new item that you can then use in the crafting. Click the items and then the "=" button.
Where do I start?
Cut the both bottles. Combine both bottles with the knife. You should have two cut bottles. Click the cut bottles under the "=" button to combine them.
I have two halves of bottle attached
Now you should tape it together. Combine the attached bottles with the tape. You will get taped bottles.
I have two bottles taped together
You need to add some water. Combine the taped bottles with the water.
I have two bottles filled with water
Then you just add pressure. Combine the bottles with water to the pump. The rocket is ready.