Here are the steps to mine Monero cryptocurrency on your WordPress site.
Sign up at https://coin-hive.com
You can follow their documentation at https://coin-hive.com/documentation/miner to manually put the JavaScipt powered Monero miner on your site.
Perhaps the best option is to use the plugin WP Monero Miner using Coin Hive.
With this WordPress plugin, you can install a widget that will mine Monero on your WordPress site. You must sign up for Coin Hive first though before fully installing the plugin.
Also, be sure to only run the cryptocurrency mining scripts on your site with the permission of users of course.
You can see this plugin in action on the site: https://tenoorja.faith/
This is a fairly simple setup. If you have lots of users on your site running this script, you might be able to mine a significant amount of Monero cryptocurrency.