Process to get accused arrested n justice to the victim

Hello Masters , Please assist me how to get the culprit behind the bars and have the justice tp my sister..The guilty , Vicky has been assualting my sister physically and mentally since 7 months..He has been circulating pics on social media using means like whatsapp and facebook owning a fake account on my sisters name, uploaded the account with her pics.He also assauled her visting her work place, life threating calls to her..Recently she got engagaged and the culprit Vicky called her inlaws and threatened them to kill them all n my sister as well and also send them her pics using whatsapp and facebook.As a result , the marriage was broken and now she is mentally disturbed and my family is scared that she might try to harm herself out of the depression. we have lodged a F.I.R in which police has regustered the case undee section 354D ,506 ipc and section 66A, 66D under IT act but still the culprit has not been arrested on the same day of F.I.R. Kindly advise what all strict sections we can file against him to put him behind the bars for bars for longest period of time and save my sister from getting attacked from him and stop his attempt to break her marriage going forward. Your all quick advise will truely save any more mishaps and get the culprit charged asap.