The plugins are added via Dashboard > Plugins > Add New or, if you have a zip-file, unzip it to your local machine then FTP it to wp
-content/plugins and make sure you've uploaded the full folder, not the folder contents. You'll need to see something like wp
-content/plugins/yournewfolder with all the folder contents inside that.
As for the application of the accordion, you can apply a universal or full-width sidebar in your template, then apply the accordion in there. If it creates a widget, simply slide it into that sidebar. If not, and you must use shortcode, just paste the shortcode into a text widget in the sidebar.