• How to divorce my wife living alone for last 3 years

Sir, 
Before three and half years back, my wife was in relationship, which I don't know, but once people living in my colony aware me about that but she deny for that. After six month, When I left from my office at 10 O'clock at night, all mohalla was gathered in front of my house and my wife was in the home, They told me that my wife was with her boyfriend alone near yamuna pusta and people caught them and they beat the boy and took in written about the relationship between them and signed all people about 20 nos. It happened 3 years back, and I left my wife since then, She was with her parent home 1 years with my 2 children. After one year, she try to come back, but I accept her by saying that if you are true file case either on me, or the people, or your boy friend who has given in written about your relationship with him and she left and file a case in CAW on me, after 2 hearing, when lady police read the letter and told my wife about the fact, immediately she drawback the case and left the 2 children with me and go back to her parents home. As well as my knowledge, she is not living with her parents. 
Please tell me how to file the case for divorce.