How to add background image behind container

Question

So i am currently working on a small assignment we have in school as practice but i don't know how to add a background image behind container. Here is a example i found quickly of what i want to achieve, note the background image http://www.njuskalo.hr. I tried adding a background image to body but that doesn't work either. Also i made two new div tags (.left and .right) to try and add it on the sides of container, also didn't work. Here is my code: http://textuploader.com/d5j5d Also note that i changed and erased a lot of stuff trying other things. And please go easy i know the code is a mess but it's something i am doing at the last minute so feel free to point out all the mistakes.

Answer 1

A background image is done like this:

.container {
  background-image: url("../images/backgroundImageLocation.jpg");
}

body{
  background-image: url("http://image.flaticon.com/teams/1-freepik.jpg");
  background-repeat: repeat;
  background-size: 50px;
  }
.container {
  position: relative;
  margin-left: auto;
  margin-right: auto;
  margin-top: 100px;
  width: 200px;
  height: 200px;
  background-color: pink;
}
.left {
  position: absolute;
  left: -100px;
  width: 100px;
  height: 200px;
  background-color: red;
}
.right {
  position: absolute;
  right: -100px;
  width: 100px;
  height: 200px;
  background-color: green;
}

  <div class="container">
    <div class="left"></div>
    <div class="right"></div>
</div>