Dear Student,
Glad to hear that after completion of your graduation and post graduation from a reputed college you still wish to pursue your interest and passion for law. For it you'll have to again pursue your post graduation in law, as you have already completed your BBA you shall go for LLB from any reputed college in India, for securing a seat in any reputed college in India you have appear for entrances like CLAT and DU LLB. After getting admission you can pursue your LLB which is a 2 year course.
Hope this might help you.