Installing a new version of the theme, is almost the same as installing a new theme. You may update your theme by downloading a fresh copy from ThemeForest, deleting the current version you have on your server and uploading the new version. For more information about installing themes, please follow this url.
Updating Required Plugins
Installing the new version of a required plugin, is pretty much the same as installing any new plugin. You can update the required plugin by removing the current version of the plugin you have on your server and go to Appearance→Install Plugins to install the newer version.