How to attach letsencrypt to a shared hosting site?

Question

Digital certificates

There is a static site on Selectel. There, in the settings, you can upload a certificate, it says "To bind a certificate, you need to generate a pem file by combining the certificate, intermediate certificates (if any) and the private key. ".
How to generate such a file?

Answer 1

found the answer all of a sudden on letsencrypt itself
https://certbot.eff.org/docs/using.html#manual

Answer 2

https://habr.com/company/zimbra/blog/345844/