Add the Code Plugin and, then copy / paste the below code to the body part of the plugin.

Note: don't forget to change the copy right ;)

<div style="position:absolute; right:0; bottom:0; background-color: rgba(0,0,0,.7); color:#ccc; font-size:10px; padding: 0  5px 0 5px;">
 © <script>document.write(new Date().getFullYear())</script> Power by <a href="https://gothru.co/" target="_blank" style="color:blue">GoThru</a>&nbsp;&nbsp;
</div>