I want a divorce

Sir, My name is Tamal Chowdhury, a 31 years old person from West Bengal. And the name of my spouse is Indrani Chaki. We have been in a relationship since 1999. And got married in 2009. But started living under a roof from 2010. Since then, my spouse have involved in several extra marital affairs (At least 4 times as per my knowledge and every time she was caught by me). Though i don't have proof of the previous affairs, but the last affair was caught on 29th April, 2014. Next day, I have recorded a conversation between me and her in which she admitted the fact. Every time when her affairs got caught she used to emotionally blackmailing me. But this time, It won't work. I really want a divorce from her. Moreover, when I told her that I want a divorce, she threatened me that she will commit suicide. Now. Sir, my question is, what is the legal procedure to file for a divorce? How much time does it take to get divorced? And most importantly, what shall be my immediate step to avoid unpleasant situation that may occur due to her threat of committing suicide? Thanks in advance.