There are many ways to do this (allegedly), but here’s how I’ve vertically aligned an element inside a div:

In CSS:

.center { 
    height: 200px;
    position: relative;
}

.center p {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
}

In HTML:

<div class="center">
  <p>This should be centered</p>
</div>