"We are putting the bottles into the big box."
Translation:Wkładamy butelki do dużego pudełka.
Not exactly. It's maybe not totally impossible here, but it's better to keep to the distinction. You can read more about it here: https://www.duolingo.com/comment/16003748/Difference-between-wk%C5%82ada%C4%87-and-k%C5%82a%C5%9B%C4%87
That's just what Polish rather uses in such cases (putting X into Y), although somewhere in the back of my head I have a thought that maybe there are contexts in which "w" would be okay... the thing that comes to my mind is "wkładać pudełko w pudełko", which would be putting a box into another box, that is probably just a bit bigger.