Hello i want to know how do enter in car (what script to i need to use) and how can i ride with car and what controls does it has
There is no out-of-the-box script for this. You will have to write your own.
But as for creating mountable vehicles -
You will have to have a car object with a rigid body, and a player object with a rigid body. Unity has tutorials in their resources section for both, actually, which is a good place to start.