Solved

How do i use research?

I have no idea how to use research points , can someone tell me how

You mean how to spend them?
If so, go into the "car" tab, halfway down you'll see the "upgrade" button. From there you decide how to spend your points.

Exactly, you decide which you want to spend your points on by clicking the +, look out you don't use more than you have, as the game won't save it and you have to do it again. You can look how much you have by reading the bar in the top when in the upgrade tab, this one turns red when you use too much.