In order to earn a college degree, you will need to earn college credit hours; each degree program will have different requirements for how many credit hours you need to fulfill, and in what categories these credits must fall. There are several ways to earn college credit hours, and most involve enrolling at a college or university, which means you will first need to complete a high school education or equivalent qualification. It is possible, however, to earn credits while you are still in high school, though this is not a common practice.
While you are in high school, you may be able to earn college credit hours by taking classes at a local community college or university. You will need to get approval to do so from your guidance counselor, principal, or teachers before this is an option for you, and this process is generally reserved for academically advanced students only. You will still need to submit your transcripts to the college or university, and based on the college's assessment of your credentials, you will either be deemed eligible or ineligible to earn college credit hours from that institution. If you are accepted, you will take classes on campus and the credits you earn will be valid toward a degree program at that college or, in some cases, at other colleges.
You can also participate in an internship program while you are in school. Internships are essentially job training periods in which you will work for a company, business, non-profit, or other organization for a determined period of time. The work you do will usually be unpaid, but you can earn college credits, thereby fulfilling various requirements you will need to tackle in order to earn your degree. Completion of the internship is usually a requirement in order for the credits to be awarded.
Aside from attending college courses to earn college credit hours, you can also earn credits by taking examinations, thereby "testing out" of certain classes. If, for example, you are confident that your grades and knowledge will allow you to bypass an introductory English class, you can take an examination administered by the college or university. If you pass the examination, you will be awarded the college credit hours you would have otherwise earned by attending the classes, but you will not have to actually take the introductory classes from which you tested out. You must pass the examination the first time in order to test out of such classes.