.m file

- (MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay
{
	if ([overlay isKindOfClass:[MKPolygon class]])
	{
		MKPolygonView* aView = [[MKPolygonView alloc]initWithPolygon:(MKPolygon*)overlay];
		aView.fillColor = [[UIColor cyanColor] colorWithAlphaComponent:0.2];
		aView.strokeColor = [[UIColor blueColor] colorWithAlphaComponent:0.7];
		aView.lineWidth = 3;
		return aView;
	}
	return nil;
}

.m file (viewdidload)

- (void)viewDidLoad
{   
    // Adds a polygon over the commuter parking in front of the library
    CLLocationCoordinate2D libComPark[4];
    
    libComPark[0] = CLLocationCoordinate2DMake(33.874689,-98.520148);
    libComPark[1] = CLLocationCoordinate2DMake(33.87469,-98.519692);
    libComPark[2] = CLLocationCoordinate2DMake(33.874314,-98.519687);
    libComPark[3] = CLLocationCoordinate2DMake(33.874316,-98.520146);
    
    MKPolygon *polLibcomPark = [MKPolygon polygonWithCoordinates:libComPark count:4];
    
    [msuMap addOverlay:polLibcomPark];
    
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

Directions

Declare an array that will hold the coordinates within the viewDidLoad function/method. Then fill the array with the coordinates. Then define a MKPolygon pointer that will use that array. Last, add the overlay to the map.