To enable HTTPS on your website, you need to get a certificate (a type of file) from a Certificate Authority (CA). Let’s Encrypt is a CA. In order to get a certificate for your website’s domain from Let’s Encrypt, you have to demonstrate control over the domain. With Let’s Encrypt, you do this using software that uses the ACME protocol which typically runs on your web host.
This is irrelevant. You can also submit your premise without your cookies. Let's imagine, you just need to type your username in the submit a new premise form in this website, and argument will be sent for your username.