how to add script code for thumb slide in slider for mobile

<script>
var slideIndex = 0;
showSlides();
var slides,dots;

function showSlides() {
    var i;
    slides = document.getElementsByClassName("mySlides");
    dots = document.getElementsByClassName("dot");
    for (i = 0; i < slides.length; i++) {
       slides[i].style.display = "none";  
    }
    slideIndex++;
    if (slideIndex> slides.length) {slideIndex = 1}    
    for (i = 0; i < dots.length; i++) {
        dots[i].className = dots[i].className.replace(" active", "");
    }
    slides[slideIndex-1].style.display = "block";  
    dots[slideIndex-1].className += " active";
    setTimeout(showSlides, 6000); // Change image every 6 seconds
}

function plusSlides(position) {
    slideIndex +=position;
    if (slideIndex> slides.length) {slideIndex = 1}
    else if(slideIndex<1){slideIndex = slides.length}
    for (i = 0; i < slides.length; i++) {
       slides[i].style.display = "none";  
    }
    for (i = 0; i < dots.length; i++) {
        dots[i].className = dots[i].className.replace(" active", "");
    }
    slides[slideIndex-1].style.display = "block";  
    dots[slideIndex-1].className += " active";
}

function currentSlide(index) {
    if (index> slides.length) {index = 1}
    else if(index<1){index = slides.length}
    for (i = 0; i < slides.length; i++) {
       slides[i].style.display = "none";  
    }
    for (i = 0; i < dots.length; i++) {
        dots[i].className = dots[i].className.replace(" active", "");
    }
    slides[index-1].style.display = "block";  
    dots[index-1].className += " active";
}
</script>