To install a new plugin, you need to go to the plugin marketplace or upload it directly to your website. (global)
The plugin marketplace is found when you go to the navigation sidebar menu on the left, clicking on “Plugins” and “Add New”. It will show up a list of plugins and a search bar.
To upload your plugin, in case you have downloaded it elsewhere, simply click the “Upload Plugin” button.
To manage your plugins, you can select “Plugins” on the sidebar navigation menu and click on “Installed Plugins”. You can deactivate, delete and update your plugins.
Also, some plugins display the Settings option from there.