You need to change your stage.html to hide divs you don't want and stage.css to style the html you do want.
Here's mine currently if you want a starting point. https://github.com/North-Country-Chapel/openlp/tree/main/lowerthird
Under stage.html the <!-- --> comments out a div so they don't show up. So this example will not show the clock but will show the notes:
<!-- <div id="clock"></div> --> <div id="notes"></div>
The CSS under #currentslide is the most relevant and you'll want to change that to whatever position/fonts/colors/sizes are appropriate for you. Check out Chrome or Firefox inspector to experiment with theCSS.
My stage.js is altered to not show video and image thumbnails and titles but the titles still flashing up there because I'm not good at rendering and DOM. You might need to add file types to this line if you use other file types you want hidden:
if ( ["mp4", "png", "gif", "jpg", "jpeg", "wmv", "pptx", "pdf"].some((char) => text.endsWith(char) )
Hope this helps.