You don't take prenursing, but rather prenursing is a bunch of prerequisites needed to get accepted to actual nursing school. for example, I am currently accepted as a prenursing student while I complete my prerequisites in hopes of being accepted into a bsn nursing school.
Check your school's website to see what classes you need to take before applying to the nursing program. Some schools have a pre nursing course you have to take before applying. I took one at a CC in MD. We learned about nursing history and how we should prepare ourselves for the next few years of nursing school. Unfortunately I moved to VA so I didn't apply.
Pre-nursing means that you are taking prerequisite courses to apply to the nursing program. It takes about 2 years to do them and then you apply to the school's nursing program and take the admissions exam as well. Basic pre nursing classes are anatomy and physiology, biology, microbiology, chemistry, math, psychology....it varies by school. Talk to your counselor and they can give you all the fine details.