a:after {
content: '';
display: inline-block;
vertical-align: middle;
width: 20px;
height: 20px;
background: url(https://img.icons8.com/material-sharp/24/000000/circled-play.png) center / cover no-repeat;
margin-left: 5px;
}
<a href="#">Watch video</a>
a {
display :flex;
align-items:center;
}
a:after {
content: '';
display: inline-block;
width: 20px;
height: 20px;
background: url(https://img.icons8.com/material-sharp/24/000000/circled-play.png) center / cover no-repeat;
margin-left: 5px;
}
<a href="#">Watch video</a>