Hello,
Thanks for using our theme.
If you want to update plugins, it can be done via Dashboard or via FTP – https://www.8theme.com/documentation/xstore/plugins/plugins-update/
If you want to install plugins, go to XStore > Plugin Installer, or in case if automatic plugin installation fails (as a rule it is because of your server settings), you can install them manually via your Dashboard: Plugins > Add New > Upload Plugin > Browse plugins archives. Or via FTP, by uploading and extracting the plugin zip files into wp-content/plugins folder.
You can find the zip files for plugins installation here – https://www.8theme.com/downloads/
Let us know if you need any further assistance
Regards