How to stick it on the tank?
You can use glue or tape to stick the background to the outside of the tank, then smooth it gently with your hands.
How to get the creases out?
Items will be sent folded.So there may be some creases. You could deal with these ways:
1) Roll it up tightly with a cylinder for 3-5 days, it will be okay.
2) Heat it with a steam iron on the back of item, then it will be smooth.