For Parallels Plesk Panel version 7.x, 8.x:
Server -> Certificates -> Add New Certificate
For Parallels Plesk Panel version 9.x:
Settings -> SSL Certificates -> Add SSL Certificate
Fill in required preferences and click button {Self-Signed}
New self-signed SSL certificate will be created in server certificate repository.
To assign this SSL certificate for securing your Parallels Plesk [...]