Login in Plesk Control Panel.
Go to Domains , it will list domains in control panel .
Find & Click on Manage Hosting in front of Domains.
Click on Applications , it will list the applications.
Click on All Available Applications > Collaboration
Select the Wordpress application and click on Install.
Check to accept term & condition and click on Next.
Specify the location where Wordpress will install and fill the setting information and now click Install.
Wordpress has been installed. Click on Administrative Interface for admin section & Click on blog for blog.