Site_Footer.html

<!-- Script Description -->

<!-- Fluidbox Integration for Image click lightboxes
https://forum.ghost.org/t/fluidbox-integration-for-image-click-lightboxes/7451 -->
<script async src="https://cdn.jsdelivr.net/gh/coreysnyder04/fluidbox-ghost-blog-plugin@0.1.0/fluidbox-ghost-blog-plugin.min.js"></script>

<script>
  window.fluidboxGhostConfig = {
    theme: 'image-backdrop', // Options: light, dark, image-backdrop, hsla(262, 100%, 82%, 0.6)
    showCaption: true, // Sets whether to capture the caption and show it below the image when expanded
  }
</script>

<!-- simpleanalytics since 2019-06-02 -->
<script async defer src="https://cdn.simpleanalytics.io/hello.js"></script> 
<noscript><img src="https://api.simpleanalytics.io/hello.gif" alt=""></noscript>

Where to add it?