1)I have got 89.80% in 10th and 67.77 in 12th and graduation (BSc)is in running in last year. so, what I have to do for MBA after graduation.

2) first we have to clear CAT course for getting admission in MBA.correct.

3)But after Completing the CAT course and all the tests,in which collage i get the admission.such as government or private or it depends on how many marks i have got in examination.

Any student with a minimum aggregate score of 50% (general category) and 45% (reserved category) in his/her graduation or degree exam from a recognised university is eligible for an MBA degree. Final year students are also eligible for applying in the entrance exams for MBA.

• IIM ADMISSION CRITERIA-
  

All the IIMs basically folow 2 steps for admission-
1. CAT
2. Written Ability test and PI
A general Category student need to score around 80 percentile overall in CAT in order to get admission in IITs. 60 to 70 percentile for SC and ST students.




You can get all information about admission in IIMs all over India from this link-
https://www.google.com/amp/s/bschool.careers360.com/articles/iim-admission-criteria/amp