In order to get admission in top B Schools you need to apply the entrance exam CAT, CMAT, MAT, XAT etc. and other University level exam also. As per the eligibility you should be Graduate in any of the field. You can also refer below given article to know the other exams & its eligibility.
https://bschool.careers360.com/articles/top-mba-entrance-exams-you-must-take

You can also check the top MBA colleges with the given below link.

https://bschool.careers360.com/colleges/ranking/2018

Good Luck!