First login to your joomla administratior.
Go to Extensions -> Manage -> Discover
Click Discover button (left top)
After few seconds you should see 3 or 4 plugins with names starting with "Installer - Install from ..."
Click checkbox for all or just for Installer - Install from Upload.
Then click Install button at the top
Now you have to enable them.
Go to Extensions -> Plugins and there find all plugins with "Installer" name , next you should enable them。
No installation plugin has been enabled - How to fix it
