Installing Ghost in Plesk 12 panel is easy, just install JXcore Plesk for Node extension and ready.
1) Install JXcore Plesk for Node from menu: Extensions > Extensions Catalogs > Install JXcore Plesk for Node
2) Click JXcore Plesk for Node and activate the option "Allow user to install NPM module" and clik OK:
3) Copy Ghost files to root of web folder: /var/www/domain.com/httpdocs or some other folder you defined for root of web files.
4) Write NODE_ENV=production in "Environment variables":
5) Finish, Ghost now active with Plesk panel.
Update: JXcore extension in Plesk has been deprecated and no longer available. Plesk provides new extension for Nodejs and Docker.
I wrote update: "How to Install Ghost with Node.js Extension in Plesk Onyx".