Hi
Automatic updates should work like a charm if you install Envato WordPress Toolkit plugin.
[The detail instructions here](https://github.com/envato/envato-wordpress-toolkit)
The other way is manually updating, you can also get the latest version from your themeforest download page, then log in your WP admin, delete the old version, and reinstall the new version.
As always though, ensure you backup your site just in case.
Thanks