Login to Plesk
On the left sidebar, click Applications
On the Applications page, this section displays all of the applications, free and commercial, that are available for installation.
Click install drop-down and select the version you want to install
Check the terms checkbox and click next
Specify the directory you want to install your Joomla and set the administrative credentials here
Also, set up the database and the passwords
Click install to finish installation in the specified directory.