You will need to enroll in an acceptable pre-law program which usually takes 4 years and then you go to law school for a juris doctorate which takes about three years. Some schools have a 3+3 program. You may want to major in Political Science, Criminal Justice, History, or something else depending on what type of lawyer you want to be. You will have to take the LSAT and do well, this is the Law School Admissions Test. Good luck!
LSAT is not required for law school and neither is 4 years of undergraduate study. See California Bar Examiners. You do not need a Bachelor's degree for law school in some states (Cal, MI). Check the Bar of the State you wish to practice in for more info. You can also attend law school through online/distance education. This limits your practice a bit, however you can practice immediately in California and the federal court system and in most other state courts after practicing for 3-10 years. For example, in Florida, if you attended a non-aba law school (online or brick & mortar) you have to practice 10 years in another state before Florida will admit you.