It is a part of drama. One man said like below and I don't understand the bold part.
FYI, A is cheif of police and his wife is pregnant now. Now A is telling this to other policemen.
A: Because you're the ones who got all up in her head about us not being prepared. Now I’m taking baby classes and babyproofing the house, and putting
things together for it to sleep in.
Best Answer
This can be paraphrased as "assembling furniture in which the baby will be able to sleep."
First, expectant parents often will refer to the coming child as "it" in the early stages of pregnancy, since the sex of the child is unknown.
Second, furniture such as cribs are often purchased unassembled, and it's up to the parents to assemble it, "putting things together".