Prerequisites:

An already approved/verified certificate from a trusted 3rd party certificate authority.

Plesk hosting.

Steps to upload the ssl

Log into Plesk;

Go to Domains > example.com > SSL/TLS Certificates > scroll down to the More options section > then click on the Manage button under the Download or remove existing certificates:

Click Add SSL/TLS Certificate > Scroll down to the Upload the certificate as text section;

Paste each section from the certificate file into the corresponding fields, as follows:

Click Upload Certificate;

Enabling the SSL

Go to Domains > example.com > Hosting Settings

Enable the SSL support option;

On the Certificate option, select the certificate uploaded on the previous step.

Click OK

That is it, ssl is now installed on your domain name.