UCAS (Universities and Colleges Admissions Services) are the organisation responsible for managing applications to higher education courses in the UK.
On the UCAS website you can search for courses and universities, apply to university and track your application. Applicants can make up to 5 course choices.–Exceptions, for example you can only apply to 4 if you wish to study Medical, Veterinary or Dentistry course. Also, you can not apply to Oxford and Cambridge you must choose between the two.
The only way to apply is online, once you have registered, they will give you your own username and password.