PA Admin is a web application part of the AppStore Integration Service which allows users to manage the Private Repository plugins.
In order to use it first of all you need to install, configure and deploy AppStore Integration Service (Please see following documentation).
How to access the web application
After the AppStore Integration service is deployed on your server in order to access the page in browser type: "{url to your server}/configtool" ( for a better UX we recomand to use Chrome).
How to add a new private application
In order to add a new application which later will be available in Trados Studio using Private AppStore feature click on "New App" button. Following modal will appear where you need to add the name of the plugin and the Version.
Both fields are required, after the information is filled click "Add"