To install a new plugin, log in to the system as administrator and from your Administration dashboard, visit the plugins section. Over there you will be able to view a tabular list of all your plugins that are available in your eFrontPro. To install a new plugin click on the "Install plugin" button (1).
This will open up a pop up window for you to upload your plugin file. If you already have a plugin with the same name and you want to overwrite it check in the "Overwrite existing folder" option.
In order to install a plugin that is already available in the Plugins list, you can click on the Install icon (2) under the Operations column.