To install a SSL Certificate for your site, follow these steps:
1. Log in to Plesk.
2. Go to Domains > example.com > SSL/TLS Certificates > Advanced Settings.
3. On the SSL/TLS Certificates page, add your certificate:
Click Browse... to select a certificate file. Then click Upload Certificate.
Click Add SSL/TLS Certificate and scroll down to the Upload the certificate files section and upload these files. If both the certificate and the private key parts of your certificate are contained in a *.pem file (you can check it by opening the *.pem file in any text editor), just upload it twice, both as the private key and the certificate. Click Upload Certificate once finished.
Click Add SSL/TLS Certificate and scroll down to the Upload the certificate as text section. There, paste the certificate and the private key parts into the corresponding fields. Click Upload Certificate when you have finished.
4. Once the certificate is created, go to Domains > example.com > Hosting Settings and:
5. Enable SSL support and select your created SSL certificate click OK
