1/ When you already had the plugin package, extract file template (in zip) to a folder and upload “app” folder and their contents to your site (allow overwrite old files)
Example, we added 'Recipe' as new plugin.
2/ Then go to Admin Dashboard/Plugins Manager/Manager/Not Installed Plugins, find 'Recipe' plugin and press on Install button to begin installation.
3/ The progress is done, you can see your new installed plugin at Plugins List.
4/ Go to Admin Home –> Clear Global Caches