Pictures under title

https://parsival.be/parsivalnew/

Under the title, as an banner, i want to place three pictures.
I develop herefore the following code.

my two questions.
Would this code (html +css) work?
Where should i place this code? At which php file and where on this file?

<div class="header_fotos">

<a href="https://parsival.be/parsivalnew/mosselen/"target="_blank"><img src="https://parsival.be/parsivalnew/wp-content/uploads/2015/11/Banner_Mosselen_2015.jpg"/></a>

<a href="https://parsival.be/parsivalnew/"target="_blank"><img src="https://parsival.be/parsivalnew/wp-content/uploads/2015/11/logoparsival_transparant.gif"/></a>

<a href="https://blog.parsival.be/?view=magazine"target="_blank"><img src="https://parsival.be/parsivalnew/wp-content/uploads/2015/10/cropped-banner_bouw-e1445366212953.jpg"/></a>

</div>

#header_fotos{
    text-align: justify;
}

#header_fotos img {
    display: inline-block;
    width: 100px;
    height: 100px;
}

#header_fotos:after {
    content: '';
    display: inline-block;
    width: 100%;
}