You can add stuff to the footer by going to the:
website configuration => appearance => footer
path: management/settings/website#appearance/appearance-setup
And then you can paste a custom HTML by clicking in the “<>”. For example, mine is:
<div class="custom_footer_content">
<div style="display: flex; align-items: center;"><img style="width: 100%;" src="https://domain.domain/public/journals/1/pageHeaderLogoImage_pt_BR.png" alt="Logo" /></div>
</div>
The src image I took from the journal logo.
But this will not remove the standard OJS logo (in my case I choose to put side by side).
The custom CSS, like what @cager proposed you may upload in the Advanced part from Appearence.
Path: /management/settings/website#appearance/advanced
My related custom CSS is:
.custom_footer_content {
display: flex;
justify-content: space-between;
align-items: center;
}
.pkp_structure_footer {
display: flex;
justify-content: space-between;
align-items: center;
}
.pkp_structure_footer_wrapper {
background-color: #081434;
}
.pkp_footer_content {
display: flex;
align-items: center;
}
.pkp_brand_footer img {
filter: invert(1);
}
The result:
