If you are updating the theme on an existing installation there are some steps which you might need to take for a seamless update experience.
Download latest version of the theme from Themeforest.
Replace existing theme folder on your installation with latest theme version.
Go to "Appearance -> Install Plugins" and see if any plugin requires an update, if so update the plugin(s).
There could be some other release-specific instructions for updating the theme (not applicable to all versions), for this read "Release Notes" section of this documentation. - Upgrading to v1.6.0 - Upgrading to v1.4.0