Umm, the question pretty much describes it.
School...really, who wants an under educated ranger making life and death decisions miles out in the country or wilderness?...start with an eduction...in the meantime apply for entry level park aid jobs, volunteer if needed, there are training centers that you can put yourself thru, Universities that have recreation or environmental programs...community colleges. Once you have yourself and entry level job, dont get an attitude, no job is too small or menial,..and yes, ask one!
Next time you see a park ranger, ask them or if there is some place that specializes in taking care of the environment in your area, try them.