I understand...

///////////////////////////////
#include <acknex.h>
#include <default.c>

///////////////////////////////

function main()
{
level_load ("work18.wmb");
}

action move_me()
{
while (!key_s) wait (1); // wait until the player presses the [S] key
while (1)
{
my.x += 15 * time_step; // move the entity along the x axis
my.z += 3 * time_step;
wait (1);
}

I would also like to know how the player is assigned to the car

Peace