It's close, but there are a few more steps than that. You need an ACME client. It sounds like you probably want a web-based ACME client, of which there is some discussion at Web browser based ACME clients.
If you do go that route (and again, I suspect your time is better spent switching hosting providers), you'll need to not only paste the CSR, you'll also have to upload a one-time file to your site to prove that the site is yours. Then your ACME client will be able to finish the certificate request and give you a certificate to upload to your hosting provider.