<a class="btn">
  こちらをクリック
</a>

.btn {
  display: block;
  width: 200px;
  height: 40px;
  line-height: 40px;
  background: #444;
  color: #fff;
  text-align: center;
  border-radius: 8px;
  margin: 0 0 16px;
}
.btn::after {
  font-family: "Font Awesome 5 Free";
  content: "\f105";
  font-weight: bold;
  float: right;
  margin-right: 8px;
}