Hey,
In India,you cannot directly become a Bank Manager. You need to clear the entrance examination of various banks for lower posts. After certain point of time,you will get promotion. Banks also conduct various entrance exams for their employees and those who clear it can become the manager.
There are two ways at present to be a Bank Manager:
The candidate needs to enter the bank as an Assistant or clerical  employee and then progressing with internal promotions;
The  candidates can also enter the bank as a direct recruit bank officer or Probationary Officer (PO) or Management Trainees(MT)and then progressing to become manager after some years of service, or progressing to various scales of officer post and progressing towards various Managerial scales.
We shall discuss on the PO recruitment and internal promotion route as to become manager; one has to first become a bank officer.
Hope this helps.
Good luck.