Dear aspirant, 

For admission in MBA following steps are necessary :

1) You have to first apply for MBA entrance exam - CAT , XAT ,NMAT etc:

2) After your results are declared , then you have to just register your application in different colleges 

3) Your selection procedure will on the basis of your 10th , 12th std and your graduation percentage  and your CAT entrance exam and your Written ability test and personal interview (FOR IIM'S ) . Different universities have different criteria , but the basic criteria will be your graduation percentage , cat score and writtten ability test and personal interview. There is no minimum percentage required for MBA , but you have to get minimum 50% in your bachelor's degree to appear for CAT entrance exam , 45 % for SC and ST  category .  

4) You will be getting admission on the basis of CAT entrance exam .