You can install any plugin or theme from the WordPress administration panel.
Browse to the “Plugins -> Install Plugins” menu item and then click the “Add New” button to search for plugins.
Once you find a plugin, click the “Install Now” button to download and install it.
Once the plugin is installed, activate it from the “Install Plugins” page. You can also deactivate it later if you wish.
For more information about installing and managing plugins, such as Full API Access, refer to the WordPress documentation.