Yes,you need to complete your Graduate degree course and Intermediate examination with maths and Physics as a compulsory subjects. But you are from commerce background, so you are only eligible to apply for Indian Army/Indian Military academy.

If you are Interested to Join Indian military academy then you can apply for CDS Examination, this examination is conducted by UPSC, twice in a year and for this year CDS(II) if you have completed your graduation then you can apply for this examination, To apply for CDS Examination your age should between 19 to 24 years for IMA and 19 to 25 years for OTA academy. Final year appearing candidates are also eligible to apply for CDS Examination.

Hope this helps!!!!