Contact the colleges that you are interested in attending to learn about their AP credit policy. Colleges are not required to give any credit for AP classes, so if you insist on receiving college credit, you will need to choose a college that will accept your scores.
Take AP classes offered by your school or study on your own. AP tests are very challenging so it would be very difficult to do well on an AP test without taking an official class, but it is possible.
Enter the names and identification numbers (provided for you by the testing service) of the colleges that you want to send your test results as part of the exam administration. The College Board allows you to send the result to a limited number of schools for free if you designate them at this time. If you later choose to have the scores sent to other schools, you must pay a small fee.
Enroll in the college of your choice. If you have not already sent them an official copy of your AP scores, do so by contacting the College Board. The university registrar should automatically credit your transcripts based on your scores and the university policy.