I would also be sterilising before first use
Wash and sterilised before every use
I'd imagine it says to steriliser before first use. My bottles said to steriliser by soaking in boiling water for 5 minutes before first use and then sterilise in the normal way for all future uses. I would say read the manual and see what advice they give.
@Carina I used one with my first. You need to sterilise before every use. And wash after every use
I would say wash and sterilise everything first x