Before the update it is always advisable to check your current version of the theme.
Login to your admin panel and then go to Appearance > Themes and click on the theme preview to see the information.
Every time there is an update available you’ll receive an email from ThemeForest that will communicate to you the update.
Sure and you can dowload the latest version from your themeforest dowload area. Every time you will dowload the theme you will get the latest version available.
Update the theme is very simple, you just have to replace all the theme files of the old version with all new files through FTP.
Note: Remember to delete all old files and then add the new theme files. If you only replace the olds one you may encounter in errors.
If you have modified some core files of the theme if you update the theme your changes will be lost.
If you want to keep your code changes you need to use a theme child.
If you don’t have change any core file please export the theme option before the update and then import it again.
The theme update is not complete unless you also update all core theme plugins and here you can find the article.