Updating a Theme
This is straight forward if you have used a child theme.
You can download the latest version from your ThemeForest downloads section. You now have two options.
1. You can upload the theme via ftp to your server and overwrite the existing theme files.
2. In WordPress you can go to appearance/themes and delete the theme. Now simply reinstall it using the new version. Your WordPress settings/theme settings and content will remain intact.