Size of the icons?

You can use css for any adjustments you need to make beyond the settings which are available.

Example 1 – changes both icons and text

#ssb-container ul {
    font-size: 20px;
}

Example 2 – changes just the icons

#ssb-container ul li span {
    font-size: 20px;
}

Where to put css in WordPress?

Thanks!