You can update the theme to the latest version quickly by using Envato Toolkit plugin.
Please make sure you did install Envato WordPress Toolkit plugin before
To setup Envato Toolkit plugin, you need an API code from Themeforest. You will need to generate an API key to link your WordPress site to your Themeforest account.
Login to Themeforest, go to your dashboard and click on “My Settings.” The API Keys screen allows you to generate a free API key.
The plugin will now alert you to theme updates – so long as you check the toolkit settings regularly.
Click on “install automatically” beside each of your themes to automatically update them.
The toolkit settings page also allows you to install themes that you haven’t already uploaded to your site, delete ones you don’t use and view version details. You can also set up theme backups.