How to add custom copy to individual category pages

2 options to do this

Option 1. Create a new page, use Summary Block to pull events from Event Page, then you can add any text block above event

Option 2. Use Script code, each page will need a different code, with this page https://www.veganfairs.co.uk/upcoming-events?category=Devizes

Add to Settings > Advanced > Code Injection > Footer

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.1/jquery.min.js"></script>
<script src="https://d1j8mu9lowy9zf.cloudfront.net/twcsl/0.1d19/twcsl.js"></script>

<script>
  var url = window.location.href;
var lastPart = url.substr(url.lastIndexOf('/') + 1);

if (lastPart === "category=Devizes") {
   document.querySelector('body').classList.add('devizes')
}
  </script>
<style>
  .devizes .sqs-events-collection-list:before {
    content: "enter description what you want";
    display: block;
    margin-bottom: 30px;
}
</style>