That's actually a great question. In the US, our pre-licensure nursing education process is designed to produce generalists. Specialization does not happen until after licensure. As a new grad, you can aim for a job in a particular specialty, but it may be very difficult to achieve that goal due to the scarcity of new grad jobs available.
In order to be 'credentialed' in a nursing specialty, you will need to meet the requirements for certification that are set out by either the specialty organization or ANCC. All of them are require passing a "board exam" for the specialty. Many also have a specific level of experience &/or post-bac or graduate education in that specialty.
If you're aiming for peds, I strongly urge you to seek a job with a children's hospital. They are most likely to have new graduate transition programs. Other wise, you will have to probably exert a lot of effort to convince someone to give you a job on a pediatric unit in a general hospital.
Best of luck to you!!