How do I specialize?

I assume you do not have your RN yet. Alll nursing school grads in the USA sit for the same type test (NCLEX). When they pass, their primary state of residence awards them a license as a Registered Nurse. You then get hired into the area (speciality) of interest, if you can. Do a Google on nursing certifications. The ANA offers >40 for various areas and other organizations offer certifications pertaining to specific areas (cardiac, pediatrics, surgery, trauma, etc.). Most require that you work as a "generalist" (nurse without a speciality certification) for 1-2 years before being eligible to take the certification exam. If you cannot get hired into your speciality area right out of school, go into an area that will care for the same type patients to get some experience (e.g. if you want to work in cardiac cath lab you might start out in telemetry unit). But for now, there are no speciality classes to take. Once you are a nurse you will be able to attend seminars that are of interest to you. You need the basic info first, though.