.fa {
    padding: 20px;
    font-size: 30px;
    width: 50px;
    text-align: center;
    text-decoration: none;
}

<style>
.fa {
  padding: 20px;
  font-size: 30px;
  width: 50px;
  text-align: center;
  text-decoration: none;
  margin: 5px 2px;
}

.fa:hover {
    opacity: 0.7;
}

.fa-facebook {
  background: #3B5998;
  color: white;
}

Add FB button to css
Add FB button to css
