Where should anti roll bars be used in f1 type cars?

It depends on your kinematic set up and your computed values like for example one of it could be the roll stiffness'.

I wouldn't spoon-feed you on this as you've to understand it on your own before following someone else's advice whether to use it or not and where. This would eventually help you in many ways. 
You'll be in a position to firmly assert your decision in the Design Report, which I feel is the most important part of the competition and you would be totally accountable for the dynamics of your car. It would give huge returns in the testing phase while playing with stiffness and other parameters.

I would urge you to read fsae forums and other books like tune to win- Caroll Smith, Race Car Vehicle Dynamics (RCVD)- Milliken and Milliken, technical papers published by Optimum G (Claude Roulle's company). After reading all these things, infact from RCVD itself you would be in a state to conclude where to use in your car (Obviously you will have to brainstorm and take an informed decision considering your driver's skill, engine power, aero/noaero, etc).

There are many cases on FSAE forums.

And lastly, I would request all of us to not post a cliche question on fsae forums without a proper protocol (name, university name, team name, and proper description of your situation) which you'd find in the answers and questions there. It just spoils the name of Indians and the one starting the thread with the question is abused very badly.

You'd think why this is important?
Because if you go to an international competition you come to know the situation and how they misconstrue us and we would obviously not want our nation and fellow students to let us down at an international level!