how do enter car

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.

From there the actual mounting can be done by creating a script which uses FixedJoint to join 2 RigidBody objects together.

Cheers,

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See this this link and this one. All you have to do is turn off the scripts and the renderer attached to the player when he enters the car and then turn it back on and place the player next the car when he exits.