My $.02
You do not need to become a CNA first, at least it is not required. That would be a personal preference. First you have to decide if you want a BSN or ASN. You can do ASN, become an RN, and always get you BSN later, or just get your BSN first. Either way is up to you.
Then you will need to apply to the nursing school of your choice. Most schools are very competetive to get into, so do not get discouraged at first if you happen to get turned down, so either have options of schools available, or begin knocking out some pre reqs for a semester if you get turned down and then reapply.
Hope this info helps some.
Mark