As the Easy Mode section of the panel states, "In easy mode, you cannot access the files for the installation (so you can only use the themes/plugins/languages we've included), but installation, upgrades, and maintenance are all handled for you!" And then again in big red print: "WARNING! In easy mode you cannot install your own plugins or themes (though there are a number included). To have full customizability, pick advanced mode below."
You'll have to delete that installation and do the Advanced install instead.