Before you could update the theme, you must enter purchase number you got from themeforest. Navigate to Appearance > Theme Options > Theme Information & Update then enter purchase number and save the changes.
IMPORTANT : Please make a backup to the Theme Options’ settings before you update the theme. you can follow this guide to create a backup to the Theme Options’ settings : http://kb.detheme.com/knowledge-base/create-theme-options-settings-backup/
To check if any update version of Provolio Theme, navigate to Appearance > Themes
There will be Update Available link on Provolio thumbnail if there is any update version.
Click Update Available link then click update now link on popup window to start updating the theme.