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.
Delete existing version of "capstone-pro" plugin on you installation.
Upload latest version of the theme to you hosting server.
Go to "Appearance -> Install Plugins" and re-install latest version of the "capstone-pro" version listed there on the screen.
There could be some other release-specific instructions for updating the theme, for this read "Release Notes" section of this documentation.