Move icons in Header

You can set the icons to become centered at smaller screen widths using this CSS:

@media only screen and (max-width: 1023px) {
    .site-header .simple-social-icons ul {
        text-align: center;
        display: block;
        float: none;
        margin-top: 20px;
    }

    .site-header .simple-social-icons ul li {
        display: inline-block;
        float: none;
    }
}

That code can be added using a Custom CSS plugin or by editing your theme’s style.css file.