This article applies to websites hosted on our newer https://cp.blacknighthosting.com platform.
For how to see your FTP details on cp.blacknight.com please see here: https://help.blacknight.com/hc/en-us/articles/212521909-Install-WordPress-through-the-Application-Vault-
Log in to the Plesk control panel for your plan:
Once in Plesk go to: Applications > Featured Applications > Press Install beside the application you want to install
If you have an application already installed it will install to /application_name. Otherwise it will automatically install the application to the root of your website.