SSL

An SSL certificate provides the secure, encrypted connection (the padlock/https://) on your website. In Plesk you can request a free Let's Encrypt certificate under Websites & Domains → SSL/TLS Certificates.

Automatic renewal

Let's Encrypt certificates are valid for 90 days. Plesk renews them automatically well before the expiry date, as long as automatic renewal is enabled — check this after requesting.

Enforcing HTTPS

Make sure visitors always arrive via https:// by enabling the "Permanent redirect from HTTP to HTTPS" option in Plesk for the domain.