I created a new webpage that has a slide show container with 6 sides. Right now I can manually click the next/previous buttons and view next/previous slides, but I need to know how I can play them automatically with a new slide shnowing every 3 seconds.
Here is my script:
function plusSlides(n) 
 {
  showSlides(slideIndex += n);
 }
function currentSlide(n) 
 {
  showSlides(slideIndex = n);
 }
function showSlides(n) 
 {
  var i;
  var slides = document.getElementsByClassName("mySlides");
  var dots = document.getElementsByClassName("dot");
  if (n > slides.length) {slideIndex = 1}    
  if (n < 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";
}
</script>.slideshow-container {
  position: relative;
  max-width: 90%;
  margin: auto;
  animation: 30s slidy infinite; 
 
}
/* Next & previous buttons */
.prev, .next {
  cursor: pointer;
  position: absolute;
  top: 50%;
  width: auto;
  padding: 16px;
  margin-top: -22px;
  color: white;
  font-weight: bold;
  font-size: 25px;
  transition: 0.6s ease;
  border-radius: 0 3px 3px 0;
}
/* Position the "next button" to the right */
.next {
  right: 0;
  border-radius: 3px 0 0 3px;
}
/* On hover, add a black background color with a little bit see-through */
.prev:hover, .next:hover {
  background-color: rgba(0,0,0,0.8);
}
/* Caption text */
.text {
  color: white;
  font-size: 25px;
  padding: 8px 12px;
  position: absolute;
  bottom: 18px;
  width: 100%;
  text-align: center;
}
.textwbg {
  color: Black;
  font-size: 25px;
  padding: 8px 12px;
  position: absolute;
  bottom: 18px;
  width: 100%;
  text-align: center;
}
/* Number text (1/3 etc) */
.numbertext {
  color: #f2f2f2;
  font-size: 25px;
  padding: 8px 12px;
  position: absolute;
  top: 2;
}
/* The dots/bullets/indicators */
.dot {
  cursor:pointer;
  height: 13px;
  width: 13px;
  margin: 0 2px;
  background-color: #66b8ff;
  border-radius: 50%;
  display: inline-block;
  transition: background-color 0.6s ease;
}
.active, .dot:hover {
  background-color: #555;
}
/* Fading animation */
.fade {
  -webkit-animation-name: fade;
  -webkit-animation-duration: 2s;
  animation-name: fade;
  animation-duration: 3s;
}
.nextbutton {
 position: relative;
 
}<div class="slideshow-container">
 <div class="mySlides fade">
  <div class="numbertext">1 / 6</div>
  <img src="gal/a1.jpg" style="width:100%">
  <div class="text">Our Mission</div>
 </div>
 <div class="mySlides fade">
  <div class="numbertext">2 / 6</div>
  <img src="gal/a2.jpg" style="width:100%">
  <div class="textwbg">Our Doctor Pannel</div>
 </div>
 <div class="mySlides fade">
  <div class="numbertext">3 / 6</div>
  <img src="gal/a3.jpg" style="width:100%">
  <div class="textwbg">Make an Appointment</div>
 </div>
 <div class="mySlides fade">
  <div class="numbertext">4 / 6</div>
  <img src="gal/a4.jpg" style="width:100%">
  <div class="text">Friendly Environment</div>
 </div>
 <div class="mySlides fade">
  <div class="numbertext">5 / 6</div>
  <img src="gal/a5.jpg" style="width:100%">
  <div class="textwbg">24/7</div>
 </div>
 <div class="mySlides fade">
  <div class="numbertext">6 / 6</div>
  <img src="gal/a6.jpg" style="width:100%">
  <div class="textwbg">Facilities</div>
 </div>
 <a class="prev" onclick="plusSlides(-1)">O</a>
 <a class="next" onclick="plusSlides(1)">O</a>
</div>
<br>
<div style="text-align:center">
  <span class="dot" onclick="currentSlide(1)"></span> 
  <span class="dot" onclick="currentSlide(2)"></span> 
  <span class="dot" onclick="currentSlide(3)"></span> 
  <span class="dot" onclick="currentSlide(4)"></span> 
  <span class="dot" onclick="currentSlide(5)"></span> 
  <span class="dot" onclick="currentSlide(6)"></span> 
  
</div>
<script>
var slideIndex = 1;
showSlides(slideIndex); 
     
     
     
     
    