Add a New label after Product Title

Use this code to the Custom CSS box

/* Add a New label after Product Title */
h1.ProductItem-details-title {
    position: relative;
}
h1.ProductItem-details-title:after {
    content: "NEW";
    font-size: 12px;
    position: absolute;
    top: -20px;
    background-color: red;
    height: 40px;
    width: 40px;
    line-height: 40px;
    text-align: center;
    border-radius: 50%;
    color: #fff;
}

Result: