Try below code:

<body>

<canvas id="myCanvas" width="900">
Your browser does not support the HTML5 canvas tag.</canvas>

<script>
var c = document.getElementById("myCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(100, 75, 50, 0, 2 * Math.PI);
ctx.arc(250, 75, 50, 0, 2 * Math.PI);
ctx.arc(400, 75, 50, 0, 2 * Math.PI);
ctx.stroke();

</script> 

</body>

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As you are a begginer you first need to know what HTML is and what is stand for :

HTML stands for Hyper Text Markup Language, is actually used to create the webpage and the content that it has, like the images and writing.

For more i'm suggesting you following site which awesomely describes entire flow of web design, what HTML is and how to use it in web design.

https://www.instructables.com/id/Web-Designing-Basics-HTML-and-CSS/

Hello here is the code you needed:

HTML:

    <div id="container">
        <div id="leftSide">
        </div>
        <div id="rightSide">
                  <div id="circle">
        </div>
        </div>
    </div>

CSS:

#container{
    width: 600px;
    float: left;
    padding: 0;
    margin: 0 auto;
    position:relative;
}

#leftSide{
    width: 300px;
    height: 300px;
    float:left;
    background-color: blue;   
}

#rightSide{
    width: 300px;
    height: 300px;
    float:left;
    background-color: red;
}

#circle{
    width: 100px;
    height: 100px;
    background-color: black;
    position:absolute;
    border-radius:50%;
    left:0;
    top:0;
    bottom:0;
    right:0;
    margin:auto;    
}