I’m sure there are tutorials, but it isn’t overly difficult. If there is an existing site, much of it is automatic.
You create a Cloudflare account.
You add the Cloudflare plugin to each site you want to add.
You go to Cloudflare, add a url, and it will create its own DNS table.
Finally, you have to go to your registrar and change the DNS addresses (usually 2 of them) that point to your hosting site to the addresses Cloudflare provides. Cloudflare figures out your host’s addresses when it creates the new site entry.
When you make changes, you may have to enable development mode on Cloudflare to avoid its caching. That may be the biggest hassle.