How do I use the header that has struct file in C?

Question

I'm new to c and a little slow so bear with me. I was given this code as a header file and I was asked to create the Queue.c. I am confused on how to approach that.

What exactly do I do with the struct in order to initialize the queue?

I have looked online and I couldn't find what I needed in order to figure out how to implement it. I also don't know how to make the Qiterator().

#include <pthread.h>        // Provides thread-safe mutex lock
#include <stdbool.h>        // Provides boolean data type
#include "Car.h"            // Provides the required Car type structure

/* =============================================================================
 * Also use the extra field "list" to write function [Qiterator] that returns
 * a list used to traverse all the elements of the queue starting at the head
 * and ending at the tail without changing the state of the queue.
 * =============================================================================
 */
typedef struct Queue_t {
    Car **data;             // Array to hold car queue
    Car **list;             // Array to hold car list
    int capacity;           // The array (queue) capacity
    int count;              // Number of cars currently in the queue
    int tail;               // The queue tail position
    int head;               // The queue head position
} Queue;

/* 
 * Initialize the fields of a Queue structure instance.
 */
void Qinit(int n);
void Qfree();
/* =============================================================================
 * Clear the Queue.
 * =============================================================================
 */
void Qclear();
void Qenqueue(Car *car);
Car* Qserve();
Car* Qpeek();
/* ===========================================================================
 * Return a list of the queue contents and its size.
 * ===========================================================================
 */
Car** Qiterator(int *sz);
int Qcapacity();
int Qsize();
bool QisFull();
bool QisEmpty();

and the header file for car

typedef struct Car_t {
    int cid;                // The car's unique ID
    int vid;                // The in-valet's ID
    int sno;                // The parking slot number
    time_t atm;             // The time of arrival (creation)
    time_t ptm;             // The time of parking (start time)
    time_t ltm;             // The expected time to leave (end time)
    char pn[20];            // The car's image file name
    char pnf[20];           // The car's flipped-image file name
} Car;

/*
 * Initialize the newly created car by setting the following fields:
 *  - cid is set to a unique car ID.
 *  - sno is set to 0.
 *  - atm is set to the current time -- time of creation.
 *  - ltm is set to a random time limited to 180 seconds -- time to stay parked.
 *  - pn  is set to the file name of a random car image limited to 13.
 *  - pnf is set to the file name of the horizontaly flipped same image as pn.
 * =============================================================================
 */
void CarInit(Car *car);