To install a Let's Encrypt SSL certificate for a domain in Plesk, follow these steps:

1. Log in to Plesk:

   • Open your web browser and navigate to your Plesk control panel URL. Log in with your credentials.

2. Access the Domain Settings:

   • In the left-hand menu, click on "Websites & Domains" to access the domain management section.

3. Select the Domain:

   • Click on the domain for which you want to install the SSL certificate.

4. Secure the Domain:

   • Scroll down to the "Security" section and click on "SSL/TLS Certificates."

5. Get Let's Encrypt Certificate:

   • Click on "Get it free" or "Install" next to "Let's Encrypt."

6. Configure the Certificate:

   • Fill in the required information:
     • Email: Provide an email address where Let's Encrypt expiration notifications will be sent.
     • SSL support: Select the checkbox to secure the domain with SSL.

7. Select Additional Options (Optional):

   • You can choose additional options like securing the www subdomain, issuing a wildcard certificate (if supported by your hosting provider), and installing a certificate for webmail.

8. Click "Install":

   • After configuring the options, click the "Install" button.

9. Wait for Installation:

   • Plesk will now request the SSL certificate from Let's Encrypt and install it for your domain. This process may take a few moments.

10. Verify SSL Installation:

    • Once the installation is complete, Plesk will display a success message. You can then visit your domain using https:// to confirm that the SSL certificate is active and working.

That's it! Your domain should now be secured with a Let's Encrypt SSL certificate.

Please note that Let's Encrypt certificates have a validity period of 90 days. Plesk will automatically renew the certificate before it expires, as long as the domain remains hosted on the server and the Let's Encrypt extension is enabled in Plesk.