I got a C in my Higher Secondary School(HSC) Exam in Bangladesh. Now How can i study at Oxford University(UK)?

I am a Bangladeshi student studying in BBA (Bachelor of Business Administration) and it is my dream to study in Oxford University(UK). I got an 'A' (Average above 70 but bellow 80 out of 100) in Secondary School Certificate Exam(SSC -which is a local exam held nation wide for the student of cl 10) and i got a 'C'(Average above 40 but bellow 50 out of 100) in Higher Secondary Certificate exam (HSC -which is a local exam held nationwide for the student of cl 12). Now I am a student of a University and trying hard to do good result as i want to study at Oxford University as it is my dream. Up to now my University result is average 3.5 (above 80but bellow 85 out of 100). Now what are the requirements should i fulfill to study in MBA at Oxford University? Can anyone please say have i even have the chance to study there or not? If i still have a chance than how should i approach to get admit in MBA at Oxford University. Please explain me the i can fulfill my dream.