To make an image a circle, we set border-radius to half the width of an image. It only works if the image is a square though!
<head>
<link rel="stylesheet" href="style.css">
</head>
<body>
<img src="https://mimo.app/r/lighthouse.png">
</body>
img {
height: 100px;
width: 100px;
border-radius: 50px;
border: solid 5px;
}