How to Update Your Theme
The most common way to update your theme is to download it from themeforest.net and re-install. Basically:
1. Switch your theme to one of the default themes of WP.
2. Remove the theme. Your data & settings will not be deleted but it's always suggested to do a back-up.
IMPORTANT NOTE: If you've done any changes in theme files (edited the codes manually), those changes will be lost when you removed the theme. Therefore, it's always recommended to use a child theme.
3. Download the new version of your theme and install it like you're doing it for the first time.
4. Activate your theme and you're done.
BUT, there are a couple of ways more to upgrade, so we suggest you to do a Google search to find the best way for you.